Hello James.
A few musings to keep you going.
When you talk about lending such a large sum of money such as £50,000, the Bank will want security, usually a charge against your parents house. I understand that the HSBC Professional Studies Loan is officially unsecured, but it covers other professions such as law where the amounts would be smaller and the professions less risky. With £50k and a mention of a pilot career, the loan will need be secured!
Using your parents property as security is not as risky as some may say, providing they know about it of course! If you get into difficulties, you would need to talk to them, but the bank realising the value of your parents house is a very, very last resort.
With the equity release schemes, be very wary. They involve your parents signing a portion of their house over to a company in exchange for money. The interest charged by the company is very high, and is charged for the rest of your parents life span. Also, you will not be able to 'buy back' that portion of the house since it will be forever owned by the company. It is not a loan!
I know of someone who managed to loan £48,000 with HSBC with security, but only £5000 of savings. He put the leg-work in, mind you, visiting an awful lot of branches with many knock-backs.
Good luck!