DeeperBlue used to have an experienced female volunteer staff member in North Wales. I believe she was an air stewardess/air crew. She was a lovely person but tragically died in car accident some years ago. Would have been the ideal contact for you.
There are a number of forum members in. North Wales and others who visit regularly, when not locked down. So hopefully somebody will respond to this thread.
I vaguely recall some forum members trying to form a Welsh club a few years ago. That could be ideal but haven't heard much since.
Spearfishing-specific training is a viable option these days and will suit some people, others not. I think most people know which they'd prefer. I learnt by doing it and from friends on this forum who helped guide me. But I had done some snorkeling and quite a lot of open water swimming ( triathlon) before and rock climbing, including soloing, to quite a high level, so felt reasonably comfortable taking this new, potentially dangerous, activity on. I have to remind myself sometimes that not everybody (inc. my son) has that sort of background to draw on.