A lot of mine have already been mentioned. Here are some that I don't think have been mentioned yet.
Car cleaning:
Autoshine Cars - based near Blackpool, not so much a detailer, but brings back some pretty disgusting car interiors to impressive standards.
Pan The Organizer - Product comparisons and reviews from Canada.
Brand/car specific:
50sKid - BMW E46 repairs.
BMW 3 Series - E46 & E90 repairs.
Volkswizard - Mostly VW Golf content.
Jamie Orr - All sorts of VWs.
Reviews:
Big Car - Gives the background story on lots of different car models.
Overtake Films - Car reviews with decent exterior camera work.
Savagegeese - Mainly for the American car market, but they naturally also get European/Asian cars in to review. Possibly already been mentioned in this thread.
Other:
Calvin's Car Diary - Occasionally pops up on LLFs channel, but luckily keeps himself sensible and out of all of the stupidity. Runs a used car dealership and makes videos on the more interesting cars that come in, was/is slowly making an E46 M3 Touring.
Camber And Combustion - 306 GTi6, Clio RS 172 track-day content with occasional showings from other cars. They push cars pretty hard and like lift-off oversteer a lot.
Darren Lobb - Used to be mostly Peugeot 306 project content, but moved on to farming content lately. Back in the day they had a couple of knackered cars that they used to beat around (think Zip Ties with less swearing, etc.)
Flexiny - Getting old cars running that have been sat for quite a few years. All European cars.
MarkCup 70 - Content on his ownership of a Fiesta ST, Focus RS, M140i and now Porsche Cayman. Does trackdays at Goodwood.
MasterMilo - Older content was mainly about ragging knackered cars around until they die. Newer content is mostly about fixing up a tank. Content is in Dutch with subtitles.
Neutral Drop - These guys popped up in my feed this morning. Based in New York (I think) and... if you're not a fan of killing cars that look half-decent in the main then don't watch.
Reg Local - Advanced driving tips from the U.K.
TR Hamza - On first glance I thought he was going to be a lot like some of the U.K. based 'innit' YouTubers, but I think he's alright. Did a lot of project content on MK5 Golf GTIs and has lately done some casual reviews on new(er) performance cars.
VHS Rallies - Came across this today as well. Full-length uploads of various rallies that were originally sold on VHS. Think of rallies like Ulster, RAC, Lombard, etc.
I've still got some others but the content isn't quite there, and some where their driving makes LLF look like miss daisy (kind of just waiting for the police to catch up to them/the crash)
I don't watch all of the videos that the channels release, it depends what is in each video. I'd never get out of the house otherwise.