It's hard to get qualified There's basically two routes: A) Getting an apprenticeship B) Paying for a Level 2/Level 3 diploma, then getting some work to complete the NVQ.
Apprenticeships are very competitive to get, and are suited towards school leavers. Apprenticeship starts have been falling: https://jtltraining.com/news/uk-falling-thousands-short-of-electricians-from-workforce-as-numbers-stand-still/
The diploma and NVQ courses are expensive, probably a minimum of £7000, and the total to get qualified can be over £9000. The NVQ requires you to be working, and as an unqualified electrician, you can only really be an electrician's mate. There is little work available for electricians mates, and where there is work, you are expected to know how to do the job already.
The training courses are in a classroom, which doesn't teach most of the actual job. In a domestic job, you may be crawling around a loft, or crawling around under a floor to get a cable from a to b. You might be drilling through joists, or chiseling out brick or block. It's noisy, dusty, hard physical work.
In commercial / industrial jobs, you may be crawling under a floor, climbing in and out of man holes, working at height, cutting tray / ladder or pulling heavy armoured cables. It can be very repetitive, and it's noisy, hard physical work. As a subcontractor, hours could be 7AM-5PM, so if you're an hour away, you'll spend 2 hours driving and 10 hours on site, which is a very long and tiring day. The people on site are probably people who did an apprenticeship as a school leaver, so they might not have much in common with you.