late deals and bargains in school hols are incredibly difficult to find. the gove effect of no holidays in term time has seen to that.
I would start looking at the kind of holiday you want and price it up now. we do this so that when a real bargain does actually come along you can spot it straight away. we wanted some flights a few years ago and I kept checking the prices on the flights websites and putting them into a spreadsheet. then there was a sale and we genuinely got a half price flight.
have a look on the shorthaul topic as there are quite a few of the sort of places you are thinking of on there at the moment. make sure you avoid the trouble spots though. end of august will be august bank holiday so take that into account when booking dates and flights.
travel republic is pretty good as are teletext holidays.