Hi and welcome to The PPRuNe Lunatic Asylum. I am sure that you will receive many responses but here's my opinion.
At 39 you may well feel like a kid (I do and I'm nearly 67) but as we get older our brains slow down. Full-blown ATC is a demanding task requiring a great deal of study, both practical and theoretical over a longish period before one becomes competent to work "solo". Typically, at a busy ATC unit a fully-experienced controller could take 6 months or more to reach unit validation standard. There are regular competency reviews and medicals, both of which you are probably used to.
Starting in ATC at your age, with no aviation background, would be a major task. Without any doubt, NATS is the way to go in the UK. Just about everything is paid for but salary whilst training is quite low. However, if you do make it you can look forward to a salary from around £50-100k and excellent working conditions. Otherwise, there are privately run ATC courses for which one pays an arm and several legs with no guarantee of work at the end.
I wish you luck...