Law, Legislation, and Statutes
There has been much speculation as to what is required over here as well. The Isle of Man is much the same as Jersey/Guernsey in some respects, but totally different in others. As far as I am aware, neither Jersey, nor Guernsey have their own Goverment, so must at least partially follow the UK Firearms legislation.
The problem we all have is the law's 'Interpretation' of that legislation. Looking at the Firearms act over here, we too had to hold a Class 1 Firearms Certificate. But, with the help of the UKPSF, we have since had agreement with the local police force that Paintball Markers are exempt from that legislation.
I would find out if you are having these troubles due to the interpretation of the act, and contact the UKPSF if you require any assistance.