You can stay in youth hostels which are cheap. Most are in outstandingly beautiful areas of the countryside and some are by the sea.
www.yha.org.uk
Yes, it's called home. If you haven't got the money, why are you considering a holiday? You should all club together, buy an old van, some tents and sleeping bags and just travel around the UK until the fuel/money runs out.
Couchsurfing!
Spain, France and Turkey are good places to go and not too expensive
Some camp sites in Newquay will, but you will need a tent.