Do you have any information on working on an organic farm?
While we don't have the facilities to organise voluntary work ourselves, the Soil Association does have a network of working organic farms that are open to the public. A visit to one of our network farms would be the ideal way to gain some insight into the workings of an organic farm before undertaking your voluntary work.
You may also want to contact WWOOF (Worldwide Opportunities on Organic Farms) - a membership organisation with the specific purpose of enabling people to find voluntary work on organic farms.
The Soil Association also runs an organic apprenticeship scheme.