After being accepted by VSO as a volunteer, I got to know in a week or two after assessment. I attended a weekend course at Harbourne Hall in Birmingham, from Friday to Sunday, taking part in Preparing for Change and Volunteers and Development during September 2005, I believe some of the training is now done on line.
These were both very good courses intended to prepare you for the volunteer experience. A great time to meet other volunteers too. I am still in touch with the friends I made then.
Details of volunteer training are available on the VSO website.
