In Scotland there are a few things that you can do which don’t require planning permission (or a building warrant) extending a ring to add extra sockets is one of those things you can do if you have a regular 2 story house (though you do have to have a warrant for a flat)

https://www.gov.scot/publications/building-standards-technical-handbook-2019-domestic/

http://www.scotland.gov.uk/Resource/Doc/217736/0098173.pdf

Fortunately we are making a (rather nice, clean and bright) workshop for my computing projects etc in the garage and so aren’t changing the use – though as it’s a modern house with integral garage we are OK for building regs (modern concrete floor with damp proof membrane, fire course between garage and house, double walls with cavity insulation, etc. Plus I want it to remain as a garage rather than convert into a room (and I don’t want to build a wall with a window in place of the door – how would I get a motorbike in there in the future?