No - but you need to think twice
I'm mid 30's and newly qualified. I left a well paid job to train full time and am still searching for a job. You're not too old so far as I can see and much depends on your personal circumstances and how much you want it. There's no denying that in your mid 30's it's a bigger undertaking than at 22 because:
You will probably be giving up a reasonably well paid career which means losing 2-3 years significant earnings
You will probably have a mortgage which you will need to cover while training and looking for a job
You may have a partner or children to consider
In light of the above you can't easily just go home to Mum and Dad (like a 22 year old can) while you job hunt and live happily on the £50 per week jobseekers allowance because you will have higher outgoings
Fitting in studying while keeping wife and kids happy is tough and it's harder to be single minded than if you were a 22 year old bachelor with no real distractions.
To put some of this in perspective I reckon it has cost me £60 000 to train plus I have lost earnings of around £75 000 after tax so that's £130 000 I have kissed goodbye to! Or put it another way it's a 3 year old Aston Martin DB7, a secondhand Cessna and £50 000 off the mortgage!
If you want to fly so much that you can't ever envisage being content unless you shoot for your dream (which is how I feel) then go ahead. Just remember there will be a lot of stress and worry associated with this career change and there will be times when the £40k job you had before will look very attractive!
Best regards,
Desk-pilot