After reading this post I can't believe the negative and bitterly pedantic attitude taken by some people regarding a simple advice-seeking question.
My advice to you AWACS , is that this site is only one source of "help" with regard to becoming a pilot and take everything on this site with a pinch of salt. Do more research elsewhere to get a better understanding of the industry/job.
I think its difficult for someone rejected from becoming a military pilot (for whatever reason). As they are the type, who wants the military lifestyle (sports, adventure, etc) and also wants to fly.
Its a hard decision what alternate future to choose. In reality, you can't have anything, and you have to choose one dream, don't count on getting the other.
You are naive to be thinking about what you will be doing at 40. You should only really think about 10yrs ahead.
Im in a similar position to you and am going for the business jet pilot dream. After literally 6years (at college and uni) of thinking, have I decided I want the pilot dream, and will let the miltary lifestyle dream of adventure go.
If the loan is the main thing putting you off becoming a pilot, then I would say don't worry about it. As you get older you realise more the importance and need for loans. You can't always have the money at hand when you want/need it.
It may seem scary with all scaremongering going around these days about debt, but it is manageable for someone on a good salary and good with money/saving. I like to think for the £10-20K you over-pay the banks in interest, the high salary, exciting job and lifestyle will more than make up for it.
Good luck with whatever you do, don't make rash decisions and leave your options open.