Its out. I ended up using 4 teaspoons (the handles, not the scoop) instead of screwdrivers. It was no better, no progress. Then I got the pins out with pliars and the rubber bung was then more 'squishable' by the teaspoon handles and when I pushed the fat cable (the cable that goes under the trailer) the bung moved a bit in the steel cylinder and then some more until it was all the way through the NATO plug 'tunnel' -the bung, the back of the pins, and the wires were then free to check over.
The solders were all good but the wires had varying amounts of contamination and breakdown. Some have bright copper but some will need to be stripped back to find bright copper. Most of the wires are white. The earth (Pin D) was black. One of the wires was yellow with a green stripe.
To make it simple when fitting the new NATO plug and pins I have labelled each wire with its pin letter (ie A,B,C,D,E,H, I, L, M, N)(F and K were blank/empty pins and there are no G and J pins). The labels are just heatshrink. Before I heated the heatshrink I used a permanent marker to write the letter on it.