It's a surprise (that's what he wanted - a surprise).
The bike is £945 but the shop local to me can get the teal for £800 which is the very top of what we're prepared to pay.
RedPandaFluff - thanks for your encouraging comments about the colour! That's what I meant when I said his friends tend to wear either a tshirt or a pair of shorts in a bright colour. Re suspension, a few different people have said it's better to have a top of the range "hardtail" than a bottom of the range "full sus".
I did text a couple of his friends' parents to find out what their kids had but the answers utterly astonished me (bikes between £2k and £4k!).