My stepdad has just got a GT aggressor xc2 from Halfords with a Suntour XCR fork , He accepts it's not a cracking fork but the problem is he's erm how shall we say on the portly side and the fork uses about 70% of it's travel when he sits on the bike.
Does anyone know if an extra firm spring can be bought whether from suntour (or another manufacturer) to firm up the fork until he's dropped some weight?

Erm can he take the bike back and ask for a more suitable one? They really should not sell you a bike that does this.

buy a new fork, it will be cheaper in the long run

Buzz , at the price he can spend(mum has an iron grip on the finances) this is about the best bike he can get + you can't get a £400 bike with forks suitable for a 22 stone+ person.

dano surely it will be cheaper to spend £20ish on an extra firm spring that I'm more than capable of replacing? the bike will probably see more canal towpath use than anything else.

How much does he weigh? The bike has a weight limit of 18stone.