Look at what are legal Section 1 rifles in the UK:
LanTac :: Rifle Selector. AR15, M4, M16 Rifles, CMMG Straight Pull & Semi Automatic.
Based on what I've read Section 1 means you need a permit and a good reason (hunting, sporting, etc...)
Only the .22LR rifles are semi-auto the rest are bolt action. But here is the bolt action .223/5.56 in action:
LANTAC LA-R15 Raven. Straight Pull, Side Charging AR15 Rifle .223/5.56mm Caliber - YouTube
Notice the 30 round mag too?