YHA Do it 4 Real camps
The cost is £450-£599, but it's subsidised by DCSF, so you only pay £399.
(5 days - 4 nights - residential, full board, equipment, instruction etc. all included).
But if you are eligible for child tax credits it only costs £150!
AND if you are on income support, working families tax credit, free school meals, etc. it only costs £25
Concessions places do go fast though, so if you're interested get your booking in asap!