I believe that around £600k is the going rate for ETPS, and around US$700k for NTPS - it's not really self-funding territory. This of-course is for the long course.
You can do short courses at both, and you can find details on both organisation's websites. My recommendation would be to look hardest at NTPS, which is cheaper and not so geared to a single major customer as ETPS is. The only FT organisation that I know who have no history of employing NTPS trained people is the one that owns ETPS! (and even then, I bet they'd still look hard at you).
To (as a Brit) attend ETPS, IMHO, you need to be either a serving military pilot, or working for the MoD / Qinetiq as a flight test engineer - I'm not aware of anybody (British) in living memory doing it by any other route. That said, there are ETPS tutors who post on here, and I'm sure they'll correct me if I'm wrong.
You could make a fair case that going for airline pilot is not the way to become a TP. That said, it's been done - and I know two people trying hard at the moment - one is self-funding through the flight test MSc at NTPS (which is expensive, but much cheaper than the "long course") the other is self funding through a PhD developing flight test techniques. Both are full time airline first-officers, self funding, but unsurprisingly very bright and motivated (which I'm sure that you are as well).
Other things that you might do?
- Simultaneously shoot for Flight Test Engineering jobs/qualifications, and flying qualifications. Eventually try and slide from the rear/right seat as FTE into the front/left seat as a TP. This has worked for a reasonable number of people (including me), but there's no standard career path and you're unlikely to ever be TP on a big jet or fighter by that route. [Me, I've done FTEing on big jets and fast jets, and TPing on lighter singles, and it's all great fun !]
- As rather more have done, fly the big jets for a living, and test fly little aircraft for satisfaction. There are quite a lot of ATPLs who also do test flying for organisations like BMAA, PFA, EAA, or smaller manufacturers. This is really for somebody with a really strong love of little aeroplanes and who has probably owned/built their own as well as their big-jet flying.
- As others have said, join the RAF/AAC/RN, and get to fly something much much sexier than an A320 anyhow, then try for ETPS after a few tours. Your degree will help you a lot there, regardless of whether it's strictly required or not.
The bottom line - you've really really want to be in flight test. Nobody drifts into the field, and you have got to make major decisions that this is the way you want to go.
G