You need to post there to be made a Mod.
Request a Feddit.uk community
If you see a need for a community on Feddit.uk then the best advice is to start it. If you need help, then post a message requesting volunteers to pitch in on the moderating. Don't worry too much though there's plenty of people around who can advise the important thing is to get the ball rolling.
However, if you think Feddit.uk needs a community but you aren't in a position to help it get started then this is the community for you. Start a new post with the idea and then, when someone starts it they can throw a link in.
Inspired by:
One nice thing about Tesseract is it lets you add mods from the community settings (which admins can edit for any local community).
Thanks for the quick reply! Is a top-level post required, or is a comment on an existing post sufficient?