You're not mad
I would say that you are not mad, just make sure that you go into this with your eyes open. You may well have a nice pot of money but can you cope with losing it and not finding employment as a pilot?
I don’t know your personal situation with mortgage, family/ kids etc but paying for flying training at the moment is huge financial gamble and you should never gamble what you cannot afford to lose.
I would definitely advise against giving up well paid stable employment to train full time, as mentioned in an earlier reply keep the job and the income, fly at weekends/ evenings with distance learning for the written exams. You can do everything up until CPL/ MEIR without stopping work, you might even be able to get a CPL done over Summer evenings/ weekends at some schools.
Either way you can get the last part of your training done in a couple of months (weather permitting) and you would not need to start the final part until you notice a definite upturn in recruiting.
To get up until you are ready to start CPL/ MEIR should cost approx £20k and you can then defer the most expensive training until the outlook is not so bleak and you will have kept your job and income all along. If the fabled better days never arrive you will have lost far less and earned far more than if you had given up work and got everything done as fast as possible.
As for your age I don’t think that it will be a big issue if things do improve, in previous good times freshly qualified pilots in their 40s were getting employed.
A friend did his MEIR with me 2 years ago when he was 48, he then financed his own turbo prop rating and has just been offered a one year contract flying in Bangladesh at 50 years old.
Just be realistic about your age, you’ll never be a captain on an ultra long haul airline making rock star money and you must be prepared to work hard for less money than you’re on right now and to possibly move to another part of the world to achieve it.
The final choice is yours, whatever you decide to do I sincerely wish you every success.