Alex, its not just that you might lose your cash in a recession, which is when historically businesses go bust, especially those that rely on others spare cash (which they no longer have in a recession) for their survival........etc..
There is also this: What happens if, having paid for your entire couse, you find you dont get on with the instructor or with the CFI, or club attitude sucks or whatever? Believe me these things happen too, as told in many threads here on PPrune. Its not easy (or sometimes possible even) to walk away if you have invested (and thats what you are doing) your hard earned cash already.
If you must know, with regards to myself its a matter of do as I say, not what I did, as I got my PPL before I knew about PPrune, when the internet was just starting to be widely available and I actually paid for my PPL in 10 hour blocks to get a lower rate....... I would not have done this if I had seen all of the threads about flying schools going bust and students losing money. I was ignorant of the risk and I just didnt know what the UK flying scene was like.
Good luck, SD.