"....doing socially useful tasks, whether visiting the elderly or cleaning up the local park."
To put it easier, Roger, these should simply be paid forms of employment, together with many others, such as cutting the blackberry bramble along Folkestone Road and uprooting it with a spade (it won'g grow so easily again), digging up the plot with the owner's permission and planting vegetables there.
There are so many other forms of work one could think of, including cleaning river beds, repairing public railings and the list could go on and on, doing shopping for elderly people and so on....
it could all be paid for as normal employment, I fail to see why half the work that needs doing in our Country is supposed to be voluntary non-paid work.
All one needs is a District Agency that coordinates all the vacant work, carries out the training and does the auditing and central coordination work.
Here is one fine example worthy of mention:
http://www.thisiskent.co.uk/Whitstable-green-activist-believes-gardening-beat/story-18596736-detail/story.html?ito=email_newsletter_thisiskent#axzz2PgLnBSxO