I am totally against community service and prisoners working IF that work could / should be done be proper employees.
Offenders should not be taking jobs off people who want to work and the council should not be benefitting from 'free' labour.
If it were down to me, prisoners would be generating their own electricity on treadmills, rowing machines or static cycles; digging their own latrines and growing their own food.
Community service would mean contributing electricity to the national grid by physical exercise.
Those unable to do physical exercise could make fire bricks from newspapers to keep them warm while they do it.