OK sounds like I might be able to save it anyhow.
Will try a bit of thinners when I get a chance just to see.
Thinking about it, after I used the heat on the underside of the playfield, next time I cleaned with ME
the residue was a little slimey, perhaps this is a clue?

As a side note, do we have any waterbased sealers in this country that are suitable for playfields?