I need to get a new reciever for when i buy an Associated B4, i was looking at an LRP Phaser Sport 40mhz recieve (LRP88400) they're going for £35 in my LHS, what advatanges does this have over a simple reciever, apart from having one more channel?

Nothing, apart from almost certainly being cheaper to buy than the OEM receivers from Futaba, KO, Airtronics, etc.