Hi, welcome to the forums!
The governing body that officiates competitions is the
World Cube Association. You can go on their website and check the competitions tab to see if there are any comps near you. Due to the pandemic, competitions were largely put to a halt but they've been slowly coming back. It looks like the only competition in the UK for the next couple months is
Wakefield Open 2022. I don't know if that's prohibitively far for you to travel. In 2019, it looks like there were two competitions relatively close in
Weston-super-Mare and
Oakdale, so hopefully once competitions come back similarly located competitions will be available.
Across the entire WCA, there are 17 official events that can be hosted at a competition, but it's up to the organizers to decide which ones they want to host. There are no age brackets, so he would be competing with everyone else. The age range of most competitors is
roughly 10-20, although you usually have at least a few parents and younger children competing. For most events, there are time limits and cutoff times to make sure that the competition can stay on track. Usually for 3x3 the time limit is 10 minutes for a single solve so he should be well within that.
There are a list of
official regulations that he (and every competitor) should be familiar with when competing. I don't want to prioritize them since they are all important, but you'll want to absolutely make sure that you're familiar with Articles 2, 3, 5, 10, 11, A, and Y. It might seem like a lot but the regulations are intentionally written to be easily readable and understandable. There are also guidelines which can help clarify specific situations as well as a
general FAQ for more WCA related things. If you have other niche questions about the regulations there's a
thread here for just that as well where both other cubers and official delegates can help answer questions.
