My dad trained in leather-craft when he started out, way back in the early 60's, worked his way up for 20-odd years, and latterly was factory manager for Charles Letts. After that site went bust (there were no other leather factories locally, so had to change direction) he spent some time as a farm labourer to bring in money. Whilst working on that farm he was doing mechanical jobs on machinery (after having spent years DIYing on cars and bikes), and with that, learned to weld. Took the welding bit, got himself a welding course and ended up as a coded welder / fabricator / sheet metal worker for 25 years. As he put it, "pattern-drafting on sheet metal was relatively easy after years of laying out patterns on leather".
I left school at 16, trained as a mechanical fitter / toolmaker, spent a year in a furniture store, spent some time in a plant & marine engineering firm, 3 years in the sheet metal dept for a domestic appliance manufacturer (hated that), did 6 months in a fabrication firm doing steelwork for prison service (ok at first, then got bored), and spent the last 4 years in the food industry, mostly doing work for supermarket chains.
I've been "lucky" with this job in that whilst the job itself occasionally gets tedious, I've had (for 3 of the 4 years at least) a good boss, a good chargehand and we have a decent laugh which detracts from the boredom of some of the jobs. The firm has changed hands, and I'm currently doing traceability on nightshift for Asda and Aldi products and working part-time in engineering.
Don't know how easily it would fit in with your current work / shifts, my advice is get yourself onto an electrical / electronic engineering course (particularly control systems and logic controllers plus 17th edition) at college (it'll also give you a network of contacts as well) - good maintenance electricians are always in demand (esp those who can program systems and instruments).