Hi Maz, I retrained as a plumber a few years ago after 20+ years working in bike shops for sh!t wages. I trained in Bristol and the course lasted two years, the third year covered advanced plumbing such as systems design and took you to Gorgi level. We covered gas in year two so although I'm not 'qualified' I had no problem installing my own boiler a couple of years ago (perfectly legal BTW, I am considered a 'competent person' in law).
The course was very over-subscribed, people were queueing up for days so I had to wait a year to get on. I enjoyed the course, I'm quite practical so it came relatively easy to me but after a couple of years I got bored of plumbing, which, combined with slightly dodgy knees and hips, made every day a chore. I'd find myself stuck behind someones dirty old toilet and think 'this is shoot, how did I end up here? I think if I had started earlier (like 20 years!) in life I might have persevered and got somewhere with it but I found it stressful and exhausting.
Luckily I managed to persuade Company of Cyclists that they needed me, my twenty years of experience in the cycle trade hasn't gone to waste so iIm happier than I've ever been professionally.
One of the problems I had with plumbing is the enormous responsibility of working on someone's house, a simple mistake can have huge consequences, and I found myself worrying constantly about jobs I was working on.
However, I'm really glad I have the skills, I still do bits here and there, and I'm glad I got out of retail. Most of the people I trained with are doing really well and enjoying it so don't let my experience put you off.
I still have all my course materials if you're interested in borrowing them.