Even more info on this one:
UK firearms licences are quite restrictive. Not only do they tell you how many rounds of ammo of each type you can have, they also stipulate how you can use the rifles. I started out target shooting, so my FAC (Firearm Certificate = licence) at the time had a condition where I could only use my guns for target shooting on a range. No hunting. No shooting up a busted up washing machine/car/stack of watermelons on somebody's farm. After a while, I got hunting added to my licence (it's not called hunting, its called "lawful quarry") but I could only hunt on land where the police have checked it out for the caliber I'd be shooting. Then after that, I got an open certificate where I can use rifles anywhere for target or hunting, without having any land I shoot on checked out by the police. It's quite restrictive. Even with an open licence, it's not open for all my guns. I have a Lee Enfield 303 which I can only use for target.
For that 50 rounds figure, that will for sure be for someone who is only allowed to use their rifle for hunting, so they don't go through much ammo. My 6.5 Creedmoor allowance is 500 rounds as I can use it for target or hunting. You can reload, you shouldn't have to return brass. I just buy factory ammo though as I'm short enough on time already.