I have never seen a fitting with a nut on the air springs, that would certainly account for the problems you had. It would have been easier to just cut the pipe, hind sight is a wonderful thing.
Yes I should have cut the pipe for sure but I didn't know any better at the time, it had the bags on from when I bought the car. I would strongly advise anyone to check the connection on new bags before fitting and if it has this type of connection don't bother because if you ever need to remove them again you are in for a world of pain!