When he did a B plus belts for me in my previous car it was around £400 (so really a C). Take away the labour for the belts and you're around £250ish I think. The thing is he has no fixed fee, he'll just charge you for what needs doing and his time.
Right, so it'll be a 'sweary' day at FS today then, rather than a 'ranty' day. Although, after he's done the job for mrs enjybenjy I'm sure it'll be turning into a 'sweary ranty' day