Or the classic, 'you can do mine if you want'. That one really gets on my tits.
+1
i usually point out that i'll need the car for at least 3 days, and 100 quid will cover the products, probably
That said one of my neighbours came up to the mrs in sainsburys today and started asking her if i'd do his car. Got home and went round to see if he was serious - he's my favourite neighbour i'd do it foc and he'd done it and hurt his back

bit bad when he addresses the mrs as "mrs clean your car man"

just as well i'm working this weekend or he'd no doubt be signing our cards the clean car couple