Join the TA for a year?
Join as a REME veh mechanic, do your basic training which won't take too long (between a month, and a couple of months depending on what time you have free, and how long you spread it out over).
Do your basic veh mechanic course (Probably be about 2 weeks, giving you the basics for Land Rover defenders and close variants... will be almost identical to your 88).
All the while you will be paid.
Once you've been taught what you want to know, you have a few options;
Stay there and carry on learning and training
Leave and take the new knowledge with you
Wait until the end of the financial year, then leave. (This way you'll collect your annual tax free bonus... £424 in first year, and rises every year thereafter.)
Maybe it wouldn't be for you, but it's a way of doing the kind of courses you're after, all the while being paid the queens shilling.