In Mast Furling Jammed

[Greg theHijacke]

Hi All,
It too 2 years from the date I acquired my Franchini 45L for the warnings to come to fruition and the "In Mast Furling" has jammed and I can't unfurl the Mainsail.
The Halyard appears to be twisted around the foil/sail inside the top of the mast, the Halyard swivel may have corroded and jammed wrapping the halyard around the foil, the sail comes out a bit then gets very tight, I have managed to get it back in to store the sail.
I have had a rigger/sailmaker aloft for several hours picking at the halyard through the sail slot and have made some progress. There is no access into the mast head to access the halyard or halyard sheave, and the rig is mast head so the top of the mast appears to be welded on with no access.
I think the furling system is "Bamar" manual with a worm drive rope system.
Does anybody have any knowledge or experience with this issue?
I would be grateful for any advice. Regards Greg theHijacker