VNS is indeed Viners.
The meaning of the "FR" on the stock is not nailed down. It is associated with some kind of repair---but "needed" or "made" isn't clear.
My 1943 Fazakerley has an "FR" on the butt, just like yours and also retains the simple rear sight.
The rear sight is a fairly good indicator that the rifle has not been subjected to the post war rebuild program that most No4s got.
This is a good thing. Rifles in their original war dress are hard to come by, as the rebuild program seems to have been very, very thourough.
http://www.skennerton.com/index.html
Go get "BritishSmall Arms of WW2" at Ian Skennerton
's web site if you are going to collect No 4 rifles and such. It is a good way to learn to "read" British weaponry.
-----krinko