'We would never have got ourselves a house if we hadn't built our own I just wish I had been 20 years younger that's all! ' Tonight's documentary looks at some of the ways that people have helped themselves to cut the cost of a roof over their heads. You can save £2,000 to £3,000 on the cost of a house if you join a Self-Build Housing Association; mark you, it's a sweat - for two years every weekend and slackers are fined a pound an hour and have to make up the hours lost. Old houses - 100 to 150 years old - can be saved from demolition by determination and skill. In Macclesfield a group of 32 families got together and not only saved their old terrace houses but also helped to rebuild them. saving hundreds and in some cases, thousands of pounds. The programme also looks at the first experimental housing co-op for young people, due to open this month in South London; and we see what a co-operatively run group has achieved after three years' hard work starting from an initial down-payment of £50 a head. £50 for a house? 'Not quite,' says PETER HUMPHRIES , the organiser of the group, 'you put down £50, work bloody hard - then you can have a house.' Producer RAMSAY short