I don't know about the Uk, but the US has many WW II rifles available. do a google on century arms or southern ohio guns dist. Presnetly available are P-38's, a few Lugers, KAR-98K's captured by the USSR and just released. There are tons of various moisen nagants around for next to nothing along with nagant pistols.
try the following
www.odcmp.com www.centuryarms.com www.southernohioguns.com