My situation is from a slightly different angle. Originally trained and qualified as a pipeline engineer, (as well as fitting pipes together it inlcudes pipeline design, thermodynamics, heating and fluid dynamics). As work became scarcer, I decided to do domestic as well. Unfortunately none of my earlier training was transferrable to the level 2, which I found silly, having to do such basic stuff just to get the bit of paper. I did a crash course to get the level 2 paperwork, though apart from the leadwork I could about do the rest with my eyes shut.
The course didn't teach much about anything other than domestic pipefitting (which isn't much different to what I was already trained in). It didn't teach much practical stuff such as installing showers, enclosures etc. It also taught outdated practices such as the use of lead clips for securing flashings, a method which is no logner recommended by the lead industry and has been superseded by stainless clips. What I did notice was how clueless some of the other entrants were.
Granted as a company I was already fairly well established and maintained a degree of pipeline work and oil boiler work to accompany my domestic stuff. My ancestors were in the trade as well so I did have knowledge in fitting appliances, I did OK. I have seen at least 4 people with little or no prior background in the trade who have done a fast track course set up in my area. Within a year of starting up, 3 of them had packed in, and the other one had gone back to tiling and doing a bit of bathroom work. I was asked to come and fix a leak in a bathroom done by one of these guys and to be honest, the standard of workmanship was utterly appaling. The shower tray wasn't even level and wobbled when someone stood in it, and the tiles had been put on plasterboard which had become wet and disintegrated. The only way to fix it was to rip out and start again.
