Good period .303s are not too easy to find these days. Sadly a lot of them are butchered so they can be owned without a certificate. There's a reasonable market in average ones still, so if you feel you must plonk a scope on one, use one of those. You can pick one up for around the £500 mark, give or take. If you really must. But really, putting a modern scope on a Lee Enfield .303 of any flavour is akin to fitting a jet engine into a Spitfire. Just not the done thing, old bean. If you still want to, go the route that doesn't drill or otherwise ruin the rifle, so when you realise the folly of your ways, you can remedy it.
I'm with those above. Get a nice example that is, to you, pleasing to the eye and shoot it with the sights it came from the factory with. It will be fun, and you'll find that the ability to shoot accurately will be more down to you, rather than the manufacturer of a scope. Obviously the Mk1 eyeball won't be as accurate as a scoped equivalent, but imagine when sitting at the range and firing it, whether your accuracy will actually stop the imaginary enemy soldier who is charging at you at 200 yards (or whatever range your range shoots at).
If you want accuracy, then go for the latest one you can find and have a good squint down the barrel before you buy it. A No4 Mk2 that hasn't been used is arguably the best for that and, again arguably, No4 rifles have easier to use sights. They're not too cheap though. Or, as above, see if you can take out another mortgage and find a sniper variant. There are, of course "made-up" No4Ts that are a tad cheaper.
