Schools in the UK seem to be funny about letting people have their old equipment, mainly from the liability sake. If someone buys or takes an old computer from them and it sets fire to their house, it is likely that person would claim against the school and win everything. It is an unfortunate attitude that seems to have crept into meany aspects of British society.

However, that is just from an official standpoint. It is unlikely you will find a school or college openly selling off old equipment but often by asking the right people it is possible to do a deal. Some places also have technicians who check equipment for electrical safety before selling / giving away, which also helps deal with the liability issues.

For a country where the government bangs on about recycling I think more should be done in the UK to distribute and re-use old computers. Currently the vast majority go to recyclers who strip them for parts and precious metals, or they just go into landfill.