National Trust working holidays

I've just learned that the National Trust does regular working holidays, which might be a good option for folk looking for a credit crunch holiday. They run throughout England, Wales and Northern Ireland and range from 2-7 days, costing £60 upwards including food and basic accommodation. It involves doing conservation, restoration or other work on a National Trust property.

I think it sounds quite good fun and a good way to meet people too. Anyone done one of these before?