I've not posted in pprune for a while but for what it's worth my answer is....
No No and No do not do it. I retrained just over 10 years ago and the first job that paid a decent salary took me over 4 years to get, remember whilst looking for that first job you need to stay current, lets say instructing? unless you go the intergrated route (loads of cash, no promise of a job if older). Don't think you can go bck to your old job, thats not an option.... so can you afford on top of the training and possible type rating, to live on next to nothing for a few years.
A rough calculation on the back of a fag packet would tell me, my time out of paying work cost me over £100,000 on top of my training costs.
It's a very real scenario, my view is don't even try. The previous poster had it right an outsider in the National has a better chance of winning!!!
Regards and good luck.
Ohhhh it cost me my marriage as well, just a thought