You guys can't be serious!
First, you can't get a real AR in the UK; they can't be semi-auto, so they're made with no gas system, so you have to cycle them by hand. And, I'm sure bbutter can share with you the process and money to get a gun there. For those of you who think the NFA process is expensive and complicated here, you have no idea...
And, CJan_NH, imagine the reaction of OUR government if they found you receiving a package from out of the country that contained 10 pounds of C4, a Kilo of cocaine, a copy of the Koran, airline schedules, and a map of Washington DC. That's roughly the reaction bbutter would get if his government found out you sent him a set of plastic AR handguards without going through a licensed importer and all of the red tape.
The rest of the world is NOT like the US. There are international "small-arms" treaties that control shipment of everything gun-related, including things like iron sights and mag floorplates. And the UK is NOT what you'd call "understanding" about people who don't follow their rules.
Remember, this is a country where violent self-defense is essentially illegal, and where they're trying to ban everything that LOOKS like a gun.
-Troy