Having inspected the coil unit, it looks like I wont be able to repair it easily, and I cant find a source for a replacement coil.
A suggestion from a friend gave me hope though.
I have a 12 volt black and decker minicraft jigsaw, quite a good little tool but the blade is prone to bending.
I taped the jigsaw to the spiralux saw's steel bow, clamped in a spiralux blade and tested it.... It is probably better than it was before the meltdown.
I made a box to contain the jigsaw, with a heavy ply base to screw the bow bit onto. Instead of taping it to the bow, the jigsaw will be attached to the underside of the saw table. As it was late, and not wanting to annoy the neighbours, I never cut out the saw table. I will do that today and get some pics up when it is finished.