Go the the milsurp forum, down the page a little - That's where we all live!
That said:
The major flavours of Lee Enfield that saw combat in WWII would have been one of two varieties:
- Early in the war, the Rifle, Short, Magazine, Lee-Enfield No 1 Mk III* ("SMLE", or 'smelly') was still in stores from WWI days, and was not replaced until the early 40s. It has the open rear sight on the barrel, the big metal nose piece, and the 17" bayonet.
- (Correct me if I'm wrong) From 1941 onwards the Rifle No. 4 started to be issued. It looks like the silhouette on my avatar. This rifle had peep sights on the receiver (which I much prefer for accuracy, personally), and the 8" 'pig-sticker' bayonet: Looks like a giant nail. The No 4 was produced in two basic varieties: The No 4 MkI was promarily British mnufacture with a button required to remove the bolt, and the Mark i* variety was produced in canada and the U.S., which dit not require a button for bolt removal.
- Also, late in the war, the Rifle No.5, also known by commercial retailers as "the jungle cabrine", made appearance in theory for the pacific war, but didn't see much use - It was a shortenend and lightenend version of the No. 4.
You can't really verify whether or not a rifle saw combat during the war, but manufacture dates will be available on internet sources if you can get a serail number from the rifle.
Hope this helps!
There is a website "P&S militaria" which is highly regarded as a source of good quality rifles, and I see Jean there has some British No4s right now. I have never bought from him personally, but he has a great reputation on this site.
Welcome to the world of military surplus rifles!
Neal