CG, have they actually said it’ll be £100 or are you just assuming they’ll rip you off?
What SHOULD happen is the bike should be looked over and quoted when it comes in. If it’s a decent, safe bike, then yeah I’d do one small job. I might make some suggestions as to other stuff that needed doing at the time, because that’s my job! If I find something wrong, I’ll call you before I spend any more money.
But if you came to me in a busy period, then yeah, you might have to leave it with me for a few days. There’s a queue you know….!
As for ‘booking in’ well, every single bike needs to be booked in doesn’t it? That’s just being professional. I’ve then got it on the computer with the relevant info typed down so I know what to do when I get to it.
That’s the way it should work…
EDIT
I will refuse to work on a bike when the owner won’t pay to make it safe. I won’t fix a puncture, for instance, when a bike has no working brakes, unless I fix the brakes too. That’s just common sense and I’d be ripping you off taking the picture repair money rather than turning you away.