Hi Chas,
Because it is not one device but many that are affected including those that are Apple Certified, surely they, Apple, bear some responsibility to ensure that "improvements" are not going to lock out existing customers.
What is happening is that the iPad communicates and pairs with the GPS device by Blue Tooth but the problem seems to be how the GPS data is then handled by the OS before passing it on to the App that requires the data. Sometimes the device is not "seen" by the App, other times the position is incorrect or does not update. If it was just one device then I would tend to agree, that it the device manufacturers problem, but when it seems to be happening to all Blue Tooth GPS devices then, to me, it suggests that the problem lies with the OS.
As I said, it appears from other forums, including those of the GPS device manufacturers, that Apple are aware, and acknowledge the problem so hopefully we will have a fix soon, I did try and roll back to 8.2 but my iPad / iTunes was not happy and I had to revert to 8.3.
Chris