you're looking too late.
no offence but you should have started looking at least a month and a half ago. mid may i was seeing loads of stores advertising for part time summer staff.think like them.if you're a business,you want to be ready for the summer rush//loss of staff due to holiday time etc. would you start looking mid summer when most of your staff are on holiday and then have to sort everything then etc? or would you be smart and get the people ready by the time your staff are beginning to go off on holiday. i'd do the latter.
if you can,join an agency and if there are still any shops advertising, shove your cv in their faces. then after a few days if you haven't heard anything,call them and ask them and tell them you're interested.