I realise I'm prob too late Dan but this place not far from me (Chong Phli near Ao Nang) just has to be the best choice.
I know Jeff to be one of the most decent, honest & fair blokes out there. He's been going for many years already, has a v good reputation with around 50 rental bikes, all taxed/insured & fully serviced in great condition at very good prices...(I really don't think there are any better or cheaper).
I know he also offers a delivery & pick-up service but not sure if that includes the bus station...Def worth a call tho. Cheers, Ray.