Same. Want to update the firmware in the computer? Sure but you'll need to unscrew the driver's seat, unscrew the desktop PC sized ECU, unscrew its four pencil-thick battery connections, unplug its 27 connectors, unscrew the 50 screws in three slightly different sizes holding the top cover on, remove the heatsinks, unscrew the eight screws holding the motherboard in, and desolder both the 144-pin 68HCxxx chips that do all the thinking.
There's a big custom chip made by GEC Plessey that has a small flash chip beside it, but it's totally undocumented. They also make the custom chips in the door, window switch, and seat outstations. I found some very very general documentation about them but nothing enough to start picking the firmware apart.
Refitting is the reverse of removal.
Yes, I have actually already done this.