At the other end of the car, whilst removing the dash (completely this time!) I noticed that the cables going into one of the DB9 connectors were a little strained, with one snapping as I moved the connector. Fortunately it was the indicator cabling, which really doesn’t need a removable connector any more (as the switch is now situated on the dash) so a few snips and it was removed.
While I was in the vicinity, I thought “why not mod the ZX9 clocks with my GPS” and a short time later they were removed and disassembled too.