Glad you found the Scottish counterpart. As long as you're in a charity that is on the register and get SSHD's permission, you'll be fine. They will be able to tell you which positions are cleared by SSHD for non-EEA nationals; each registered charity has a person to deal with it. Generally, anything administrative, clerical, or maintenance is strictly forbidden, but exceptions can apply.
And clairelynn, the volunteer visa has been morphed into T5 Temporary with the same restrictions along with the entire draconian framework of the PBS. And yes, the old volunteer visa was horribly abused, including Americans who went walkabout after the 1st week, or never bothered to show up once they cleared immigration at the airport. Thankfully, not just Americans, everybody more or less took part.
Over time, people got angry about it. It's one of the reasons only 1 charity in the UK was willing to accept immigrants for the probationary citizenship scheme. One.

The government has had to add some 'sweeteners' to get them to buy in to it.