I used to work at sainsburys, i got 4.83 an hour but i HATED IT!! but this was mainly because my boss was made out of evil and hatred, so it would probably be ok for you.
although, their maximum contract is 12 hours a week, and on top of that they dump a lot of overtime on you which really got in the way of my exams, which was one of the main reasons i quit.
I work at matalan now and get a penny less an hour haha, but it's a price worth paying cos it's reasonable hours for someone as busy as me and the people that work there are actually my age instead of 60.
i know quite a few people that work at asda and they all seem to enjoy it
I work at sainsburys and I'm on 6.23 an hour.. But I think it was 4.85 or something before I turned 18
and about the forcing overtime on you thing...it's easy enough to just say no...and if I tell them I'm busy with school they don't even offer me it
My managers etc are all quite nice but I spose it changes from store to store
Kiln lane Epsom store is the best, loads of young people and GREAT training and loads of opportunities for overtime, I get 6.70ph and work 12 hours a week, it goes really well with my school work as well x