Ethel's calculations are near enough correct (I think she may be �1 per year out, but let's not quibble) provided your friend is paid for 52 weeks per year.
If he takes any unpaid hols his annual tax bill will be less. And don't forget he also has to pay 11% on all his earning over �104 per week for National Insurance. (This amounts to about another �371 per year - about �7.15 per week) for your friend.
Unlike Income Tax, NI is not cumulative, it is payable and non-refundable weekly or monthly (depending how you get paid). So if you pay it when you earn a full week's wages, but earn nothing the next you do not get a rebate.