I believe the 'official' method is to cut out the connectors altogether and directly solder the wires together. People are justifiably paranoid about the possibility of setting off an airbag or pretensioner, but I suspect the risk is only really there if you accidentally short one of the wires to a 12v supply. I'd be prepared to take it on after disconnecting the battery and waiting for a while for any residual voltage to discharge from the system, but if you choose to do likewise then you're on your own.
Keep it simple - cut, solder and insulate one wire at a time to eliminate the chances of getting crossed wires or shorting two together. If you don't know how to solder and don't fancy giving it a go, crimp connectors will probably be just as effective if used properly with a decent crimp tool.
My turn to be grateful
Spend the holidays over at my parents in Holland who have a nice covered area for the car so spend another day to sort out the problem once and forever. Disconnected the battery, waited 30 minutes and then started to cut the wires, one by one and soldering them together on both seats. Screwed everything back together again and after connecting the battery, the display now finally issues the magic word once more: OK