Hi Baz,
Certainly a lot of your skills and experience are transferrable to Aircraft Maintenance, I've met a couple of ex-car mechanics in the past that have successfully transitioned into the industry and turned out to be very good technicians.
In many respects a lot of the older GA aircraft have much simpler systems than your average modern car so again I don't think this is much of an issue for you.
One thing to bear in mind is that the salaries in GA tend to be very low, you might well find that you can earn more working for a franchised dealer than you would working on light aircraft.
One benefit is aircraft tend to be cleaner than cars so you'd be going home in the evening with less oil and dirt under your fingernails 😊
I'd suggest trying to find a GA company local to you and see if you could do a couple of days work experience, it would hopefully be enough to give you an insight into the job to make the decision if it's something you would like to do. They would also be able to point you in the direction of local training courses etc.
Good luck !