Spend some time browsing here. There are plenty of ideas.
And as mentioned, you can do OK with PC's if you specialize. I'm told there is still money in high end super graphic units for gamers.
I spent 10 years and did well building systems for retail Point-of-sale systems. That was in the 90's, before evryone could buy a bar code scanner on ebay. Between pint of sale and GPS fleet tracking I did quite well.
There may still be a market there, I don't know about the UK. I wired tow trucks and installed GPS units so the dispatcher could see where they were and the boss could tell if they were stealing.
Tracked each time the passenger door opened, the power takeoff was engaged, they did a jump start, hood opened and had a load sensor so they could tell if they had a load. Amazing how many tow truck drivers will stop on the road an do a tow or a jump start for cash in their pocket. Get sent to an airport parking lot, do one jump start for an auto club, three for cash and just turn in the auto club ticket.
Find a niche like that, you're good to go. Lots of fun wiring the trucks, installing the units. Big bucks, too. I had jobs from $ 40,000 to $ 80,000 with fleets. One was a fleet of office machine repair vehicles. 6 cities across a state. Boss went by an employees house at 2:30 PM and saw his truck in the drive. Spent $ 80,000 to keep them honest.
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