http://www.guardian.co.uk/money/2009...s-minimum-wage
I am sorry but I dont know an awful lot about your situation but £35 for 12 hours work seems awfully low to me. I just googled this article which seems to reflect what might be happening with your tips.
I thought that the reason why the minimum wage for food service was lower than normal was because the tips would make up the difference? Dont know if that is definitely true or not?