ULTRA- there were at least seven ULTRA codes that we know about (as ULTRA still forms the basis of some codes it is unlikely that we will ever know how many there were); Air Force, Navy & U-Boat, Foreign Office, Army & Army- West and SS. At no point in the war was every message 100% decrypted- the proportion was usually less than 50% and for some of the codes no more than 10%. the easiest codes belonged to the Air Force and the Foreign Office- being static they used harder codes (more 'wheels') but as a consequence changed them less often which made it progressively easier for Enigma to decrypt. By contrast Doenitz suspected that the U-Boat code had been broken (it actually hadn't) and thus moved to a new code system with regular setting adjustments that prevented Enigma from decrypting more than 10% of any code group for much of the war. To say that Freyberg had full access to ULTRA decrypts, regardless of how they were presented, is wrong. further, it seems likely that as we know that the Allies still expected a seaborne invasion, it would suggest that the Army and Navy codes had not been deciphered to any great extent. As the paratroops answered to the Army it is equally unlikely that detailed plans would have been available through ULTRA.
Captured Documents- Greek neutrality was largely a matter of internal politics; pro- fascist and pro-Allied elements were unable to hold enough power in order to sway the government and people firmly one way or the other. the most pro-fascist element in the government was the Inteligence service, the most likely source of any pre-invasion planning. as the evacuation of Greece preceded the planning it is unlikely that Allied intelligence was yet in a position to capture such documents. given that this was known to the Allies it is unlikely that any captured documents from such a source would have been given a full endorsement. further, since the supporting naval operations were the chief determinant of British action, and this would have been a consideration in any planning effort, and that the Royal Navy refused to engage the enemy (at least with major fleet units) under the circumstances, it is unlikely that the sort of detail required to significantly alter the Allied preparation was forthcoming.
Troops at Maleme- the hardest hit units in Greece were the New Zealanders and the Australians- first in and last out. in both cases the casualties had affected the better units and officers within those divisions. this meant that many units were short, particularly of the leadership element. as command is as much experience as it is talent, it seems more than a little unfair to blame inexperienced officers and NCO's of making mistakes in their first engagement in those roles. and as one who has made the transition from one rank to another it is difficult to fully understand the full requirements of the new rank until called upon to demonstrate those requirements; it would be more difficult as an adhoc appointment. ultimately these adhoc promotions are made by the units themselves- in due course they are endorsed by the senior commander through the advice of his support staff and confirmed by the government. unless he had sat down with every soldier on the island, and broken several regulations in the process, Freyberg had no choice but to rely on the appointments made by his subordinate officers.
also, a point often made in the diaries and journals of the troops themselves- they were still recovering from the shock of Greece when the attack began. as has become increasingly apparent from psychological studies 'fighting spirit' is eroded erratically but can only be restored by degrees. the shock of two major campaigns/ battles in the timeframe involved would have caused severe 'psychological disfunction' in a large portion of the troops engaged; particularly as they had been so comprhensively beaten in the first engagement.
Resources- Lavarack and Bennett were in such disfavour politically as before the war they had publicly, and after the war started, privately, said that the Australian Army was poorly equipped for modern warfare. The same was true of New Zealand, though i do not know of any officer who attempted to speak out. The arrival of four ill-equipped commonwealth divisions, plus assorted Indian and British Units, had effectively depleted the ready resources of the Mediterranean command. follow on resources were used up in mounting the Greek intervention; the next echelon of military stores were only just arriving or else were still on their way when battle began. this covered not only aircraft and ammunition but boots and uniforms. even requisition forms were in short supply. the evacuation from Greece had effectively denuded all the units of transport and heavy weapons- the very resources most required in order to mount an effective defence against any invasion. these 'faults' lay in the parsimony of pre-war governments in ensuring the troops were properly equipped from the outset and that sufficient stores were accumulated to last until wartime measures were enacted. Furthermore- because of the Greek political situation- it is unlikely that anyone could have requisitioned Greek supplies without upsetting the delicate balance between the two sides. although one might be tempted to argue that Greece's neutrality had been violated, the pro-fascist elements were in the ascendant and would be arguing for an accomodation with the Germans.
Command- The senior British and Australian officers had been recalled to Cairo owing to the former's failure in Greece and political considerations for the latter. of the three remaining Australian officers only Makay, a poor performing divisional commander, was available to take command. to my knowledge there was no British divisional commander available on the island or immediately despatchable- otherwise, given British sensibilities, they would have been given command already.
The Mode of Attack- for the first and last time in history an opponent proposed to attack a major target utilising only airborne and airtransportable soldiers. by this stage in the war only two major combat drops had been made by the Germans- Norway and Holland- both of which were expected to encounter nil or limited resistence with ground forces to arrive quickly by sea (Norway) or land (Holland). Allied planners raising the first airborne units on both sides of the Atlantic, and with Commando experience to guide them, suggested that such a mode of attack was so risky that it was very unlikely to be contemplated seriously. this opinion was widely circulated in order to ensure the effective use of the special forces as they became operational and to secure support for the eventual doctrine evolved. Freyberg, viewing the 'experts' opinions and with history as a guide, could not be reasonably expected to do otherwise.
finally, in the matter of spatial relations on the battlefield, the Germans had the resources before the war to think in terms of the three dimensional battlefield and put them into practice; the British and Commonwealth generals continued throughout much of the war to think in two dimensions. whenever faced with equal or superior power in the air, the third dimension, the British and Commonwealth (and French) generals performed very badly; even with air superiority they continued to think in two dimensions in its application. for example, whilst the luftwaffe continued to roam the Forward Edge of the Battlefield (FEBA) until it ceased to be a factor, the British Typhoon was conceived and developed as flying artillery or for interdiction of the first echelon of support. contrast this with equivalent American and Russian aircraft, both of whom practiced German methods. one might even contrasting Slim at Imphal with Montgomery at Market Garden; the former took an active interest in air operations whilst the latter left much of the air element to be worked out by his air staff. one could argue that by virtue of his professional shortcomings Freyberg demonstrated this in abundance; but no other British officer who emerged in the European theatre demonstrated any better understanding and several were considerably worse.
and i still don't expect that it will change your mind.