I'd say £8.00 is ok, but you aren't going to be driving a 5 series beamer anytime soon with prices like that...Mondeo man maybe?
Tenner a clean? Well a bit better, and around here you would stand a good chance of getting that...
£12.00 per clean?
Well you might get up to a 3 series beamer on that

If you could get £15.00 then you would be on very good money indeed, but you wouldn't stand a snowballs of getting that around here.
What would I charge?
I'd charge a tenner, great money if you can get a string of them, but I prefer drive betweens and bigger accounts, so I use accounts like this as fillers.
I do have a few at £8.00 but any future ones of this kind of size will be going up to a tenner.
I do some on one estate where several are at the £8.00 mark, maybe not quite the same as the house in the picture, but I think a similar amount of work, in a few months there will be a load of new people in these houses (army) and the whole lot will be going up to a tenner.
Ian