I've done very limited PPL training but my research told me this:
1, Flybe replied to an email from me when I asked if my age was a barrier to employment with them. They replied that they take pilots from all different backgrounds and that modular shouldn't be an issue and nor should my age (38).
2, Can't answer that.
3, Check out Bristol Ground School.
4, Check out Aeros's Fast Track scheme. This is run in conjunction with BGS and has placed pilots with airlines. You can do this as quick or slow as you wish.
5, I would go with Aeros if I had the funds as the Fast Track scheme is PAYG and Gloucester is 5 minutes from my house! BGS also offer a similar scheme. Links below:
Aeros Fastrack - Aeros Flight Training
https://www.wingsalliance.eu/