Amateur string players in London might be interested in some chamber music coaching sessions now being run, details at http://www.londonstringplayers.co.uk/ . I went to one evening run-through of some early Mozart quartets recently and enjoyed it a lot, even as a fairly raw player myself. It's open to all string instruments and all skill levels, as the ensemble and repertoire are tailored to match the resources available. Recommended!

This looks brilliant. Shame I am not nearer Lonodn, or there was something similar in t'North.

Looks interesting - but it seems to be only for violin and viola. What about the cellos?

Also, whereabouts in London is it?

The coordinator of the workshops also teaches violin and viola privately as a separate activity, but not cello, so that is why she mentions them but not cello. At the chamber music workshops, cellos are welcome, and are in fact indispensable! I should have said that I went as a cello player myself. For basses, they may have a role in the planned string ensemble rather than the chamber music sessions.

The area is NW6, Kensal Rise, see the "Location" link (second from the bottom) in the URL I posted for details.