in england you need a FAC if the muzzle energy of the airgun is higher than 12ftlbs. Unless you're going to be using the rifle for hunting or somewhere other than your garden, buy a .177 12ftlb gun.
also, a theoben rapid is going to cost you at least £700 to get running for the gun, silencer, scope and pump. i'm guessing it's in .25 caliber because a .22 air rifle at that energy would need specialised ammo and that's expensive, but .25 ammo is expensive too. don't waste your money, My .22LR smallbore rifle was £400. if you want a hunting weapon, at least consider a .22LR or .22 magnum. A quality smallbore rifle will perform for decades flawlessly if looked after. I've never liked air cylinder air rifles because the seals will start to leak after some use.
if you're interested in learning about shooting, i strongly recommend joining a smallbore rifle club if there's one close to you, use one of their club guns until you feel you ought to own your own. smallbore target rifle is a *very* precise sport and you'll be taught all the basics of marksmanship there, and there's a lot to learn about.
so long as you don't have a nasty criminal record and can give good reason for owning a rifle, it shouldn't be a problem.