For a tent go over to a festival site day after it finishes e.g. Glastonbury. People buy a tent for weekend and just leave them and hundreds of them, a real headache for organisers as few charities want the hassle of collecting them so they are usually quite happy for you to collect a few for local DofE or other events, quality varies from Halfords own to Blacks etc.. Bound to be some festival or other in your area soon.