Hej Mattias!
The WW I Lee Enfield (Mk III) was the same as used in the beginning of WW II as well as in the far and middle east (including Italy) during the whole war.
During WW II Rifle No 4 Mk I started to replace the Mk III rifle, this was used in the ETO fex.
Differences etc can be seen here:
http://en.wikipedia.org/wiki/Lee-Enfield
I am not sure what scale you are looking for but if its 1/35, here are your options:
Most kits of british WW II soldiers are equiped with the No 4 Mk I so cant be used.
Imho one of the best sources is actually the old Italeri Allied weapons kit, this set has three Mk III rifles.
The ICM WW I british infantrykit rifles arent very good.
Dragon has released some british desert soldiers and a set from Cassino and some Mk III rifles are included, but to be hounest I actually pefer the Italeri offering, and they are cheap to!
Hth
Erik
Sweden