If it's any help, I retrained at 42. I was fortunate to have completed an apprenticeship in control engineering in industry. Not quite the same as electrics but a lot of cross over skills. Got the 16th edition, Part P, and 2391 via short courses, then spent time with a friend leaning'house bashing' - the hardest part in reality , all on a self employed basis. I then advertised a lot and took on all the small jobs other more established electical contractors didn't really want, like changing odd sockets and lights, adding a socket in the garden etc etc. There's a surprisingly large market for such works. I built a reputation from that, which eventually led to better and bigger jobs, lots of referrals, and my first apprentice. Business expanded from that, and I took advantage of the solar market demand. 6 staff later and the joys of running that size of business came to an end when the government destroyed the solar side of the business. I should have sacked the staff at that point, but didn't really want to. Eventually I worked out that insufficient works mean't I needed to let staff go, and reducing the overheads mean't I could work 3 days a week, with no headaches, and earn the same money. So I came full circle after about 16 years, and went back to the small jobs, kitchens and bathrooms, a bit of school maintennace work and some testing and inspection for landlords. In reality the small jobs earn a higher daily rate than something like a full rewire, with plumbers and other trades charging £80-100 for an hour (or just turn up), customers don't bat an eye lid when you ask for £60 to change a socket, plus you get to go home early! Site work tends to be the more lucrative, purely because of the sheer hours you can clock, but sites come and go, so tend to be a bit 'feast or famine'.
One option for you given you already have some training would be to go 'agency' for a while to get back into the electrical side of stuff. Level 3, from memory, was mostly about producing a 'portfolio' of works to show experience gained rather than learning anything technical ie no real benefit to doing it. I've also seen the quality of agency staff on some jobs, and most leave a lot to be desired, so work hard, turn up on time, and you should be fine. Do that for a while then perhaps start your own business. Your son can work elsewhere for a few years until you are in a position to employ him within your own business.
with my level 3 I just never done my nvq but still worked on sites I still keep my hand In here and there but only my own stuff and family’s like you say sockets lights garden lights. I think what’s made getting thinking about sparking more is the face my son has got into and he’s loving he’s doing commercial stuff ie Starbucks, kfc, tacho bells also domestic stuff to so I’m just wondering would it be worth getting back on the tools well what I have left I’ve given everything to my son ha
. 
