All Fixed!!!
Thanks to the wiring diagrams (Cheers Phatgrob) the garage got it sorted. Once they new what was what the fault was traced to more melted wires tucked under the dash (had to remove fusebox, panels etc). As usual the Explorer is an enigma in relation to tech info/garage databases.
App the drain was being caused by windows, ABS, compass display all being constantly live due to the short.
The seat had caused the problem, the fuse didnt blow because instead of a 10A, there was a 30A instead!!! and the wire was rated at 12A. The seat was tested and now only draws .4A, so must be an intermittant fault caused the serge. The mechanic also tried to fix the airbag light, but that would be a whole new bill!
They had the car for a week and only charged for 5 hours work - I'm well happy with that. If anyone needs a good garage in SE Essex let me know