Hey mate, congrats on completing your first build (any pics/videos? Would love to see!).

You can head over to the Live Events section and see if there is an event that suits you date-wise. If it isn't long until whatever event you look at, somewhere in the thread there'll be a link to a signup page, where you can enter your robot into a featherweight rumble, at one of the many heavyweight events held by Robot Wars (previously Roaming Robots) and Robots Live. If the event is still some time away then a signup link will be posted closer to the date.

The other type of UK featherweight accepting events in that section are those by RoboChallenge, which in fact are solely FW. The FW championships unfortunately have a sign up number limit, which has been met for this year, but you can still go to their event on the 10th-12th of next month which is held in Yeovil.

The RoboChallenge events allow spinner robots, whereas the heavyweight shows that have featherweight rumbles do not, so you're less likely to get badly damaged at the latter. However Yeovil is a very relaxed event and if you don't want to fight a spinner you don't have to.

Sometimes an event organiser may make specific requests, but there are no requirements other than meeting the FRA rules. There is no necessary number of wins or anything, this hobby/community isn't like that. :)

Good luck, and yeah, show us your robot!