The requirements of the Online Safety Act will come into force on March 16, 2025. This will affect any hackspace which hosts their own user-to-user services like wikis, forums, etc. It appears to exclude mailing lists though.
Ofcom has recently published their regulations on what is required. Unfortunately it’s an 1800-page mess of PDFs. I’ve written a more readable summary on my blog.
I don’t think compliance will be too difficult for hackspaces running small forums or wikis (they will certainly be classed as low-risk). You will need to prepare a risk assessment before the deadline. You will probably also need to update your terms and conditions. Hopefully we’ll be able to share some templates of these here soon.