Good luck with whatever route you choose... if you're keen on learning in a taildragger there are clubs that operate Cubs, I think there used to be a cub at Cambridge that operated solely Tiger Moths. Where in the UK are you?
If you'll be doing all your flying in the UK and have no further plans for any more ratings (CPL etc.) then the NPPL is the sensible choice. Not sure why people would tell you not to learn in the DA40... you are the one who's learning and paying so it should be your choice.
As for clapped-out 40-year-old PA28s/Cessnas, your judgment is partially correct in some cases but in many cases not. Aircraft
have to be maintained to a high standard... my club has 2 PA28s and a Tomahawk (all 20-25 years old... OK not brand new but not ancient), all of which are in good condition, certainly not clapped-out or "cruddy".
P.S. If you're going to learn in a Moth or Cub then bear in mind most of those will be >60 Years old...
Smithy