Hmm, interesting one Tdm.
I started on area in 1987 and did the NE Sector which was then 126.65. I'm fairly I certainly remember transferring an aircraft leaving at Pole Hill to Border on that frequency. I should have some old documents filed away somewhere, which I'll try and find. Is it possible Ulster closed before Border and the frequency was re-allocated? I can't remember any reference to Ulster Radar in the EGCC MATS 2, but of course that in itself doesn't mean it wasn't still there.