@telectrix personally I’m quite strongly against having to be a member of some trade to buy materials for a few reasons:
1) Where does it stop? Almost any trade could tell tales of doom. Would you let people work on their own cars? Would you have to be a joiner to buy roof truss or builder to buy bricks? If you mess up fresh fresh water plumbing you can poison people with contaminated drinking water.
2) Most DIYers know their limits - plenty would change a light pendant or a few sockets but there aren’t many that would change a consumer unit etc. Can a business make a profit from changing 2 sockets?
3) The risk isn’t that great, in the past 30 years I’ve only known 2 people killed or injured from electrocution. These two were experienced professional working on a HV sub station. I don’t personally know of anyone who’s house has burnt down. More often than not when you read about electrical fires it’s not even fixed wiring that’s at fault. I’m not saying it doesn’t happen but it’s certainly not at epidemic proportions. Certainly far less common than road deaths or drink/drug related deaths.
4) lots of people are perfectly competent but don’t hold the required certificate/membership. Industrial sparks etc.
5) The people who employ Dave from the pub will still employ Dave from the pub. Often their not doing it by choice, their doing it because they don’t appreciate the dangers and can’t afford a professional. You just end up making life more expensive/awkward for those doing this legally.
6) DIYers won’t stop buying electrical gear, but they will loose access to good quality parts from reputable suppliers. Instead of fitting MK sockets from screwfix they will be fitting cheap chinese eBay specials that have little of no product testing.
In my view the best way to improve electrical safety in the UK (which is already pretty good in my opinion) would be to teach kids at school a basic understanding. Safe isolation, basic workmanship, changing sockets etc as part of design technology type subjects. Instil an appreciation of the risks and give them some practical skills has to be better than trying to ban it.