I spent a few weekends helping the volunteers early this year. It's volunteers on a w/e and crimmo's from agecroft nick of a week - passing pedestrians are apt to be confused and shout abuse at the volunteers by mistake !
Anyhow, the volunteers are a great friendly crowd, and every few w/e's a buffet is laid on at lunch.
We helped clear offcuts and branches from felled trees which have ntaurally grown in the bed, and spent much time scraping out grass from between the cobbles ("sets") - this latter exercise a tad peeving as noone qualified to then spray weedkiller (eg: Cart ?) actually does so, therefore the grass grows back ! This was suggested partly due to wildlife concerns, but I wasn't convinced. I suggested some nightime guerilla weedkilling... All that said, the MB&B volunteers keep up the work, as their contribution, even if a little lightweight, does much politically to attract sponsors, keep up the pressure on other "stakeholders", and keep the resto effort alive in these straitened times.
Pip pip Norm
see also http://www.bbc.co.uk/arts/yourpaintings/paintings/barges-on-a-canal-107275