I need some extra cash, where is the best place to look for cash-in-hand work or flexible part time jobs, i can't easily do a set day etc as I work an odd 21 day shift pattern

, Don't mind anything really, but prefer driving/ labouring/ mechanics etc- I am an aircraft engineer in the RAF so I can turn my hands to most things, but I just want somthing thats going to pay £50ish a day cash in hand or £10 an hour ish....?? Any ideas where the best place to look is?

Am in the West mids if anyone knows of any work going