I've just had the hinges of 7 doors replaced in my house. The carpenter invoiced me ahead for the materials - £110 for 21 hinges, which I paid in advance. When he came to do the job, he only used 14 of them. Should I ask for some money back (or rather, off the labour cost, which I'm about to pay), or ask to keep the hinges that weren't used - or just forget it (if I'm being petty)? Is this standard practice? (Is £110 a lot for 21 hinges?!)