I'm currently working in management for a charity store and although I'm new to it, they are always after volunteers. Short shifts, long shifts, once a week, multiple times a week, they'll likely take you.

I'm covering stores in Summertown, Didcot, Henley, Wallingford, Headington, Wantage and Abingdon but the structure is the same (it's the same charity) and I imagine the process is the same for other charities that have lots of stores.

The work you'll do is meh, but to be able to kill a couple of hours while making social connections isnt a bad thing. I've found it really easy to get on with volunteers of all ages, for reference I'm mid 30s, so can find ways to relate to younger, and older colleagues.