TBH, your friend will find it really tough to do postgraduate research. Sorry to be blunt. Yes he will probably be able to get onto a masters course but even if he gets a distinction in his masters, he still would not be eligible for any PhD funding that I'm aware of. Realistically, he would have to self fund his way through a PhD.
Honestly, his best bet if he's serious about going into research is to go back to basics and do another BSc - mind you, it would have to be in a different subject. I think this route would result in far less debt. If he works hard and tries to get research placements booked for every Summer holidays and then gets a good 2.1 or a 1st then he'd probably be able to get onto a funded PhD without having to do a masters course.
If he were to do an MSc and then self fund a part time PhD then it would take him 5-8 years of debt building times to become qualified. Chances are he wouldn't be able to do his research in a department with a good reputation and in the sciences, part time students can often be treated like second class citizens. If he starts a new BSc and makes sure to work hard then he could get qualified with a PhD in 6-7 years with only three of those years being debt incurring.
I know that it sounds incredibly depressing to think about possibly going back and doing undergraduate level again but it would be a hell of a lot less depressing than having to give up his dreams after he realises that he can't afford or can't get even a self-funded part time place after an MSc. I know of two people who have gone this route and I would strongly advise anyone else to consider doing the same.