gap on the autobox selector? do you mean there is a gap down the side or where the indicator strip should be? cos i think i have a brand new indicator strip in the garage somewhere!!
The gap is down the middle? Ie you have the handle and flap to lift and select gear, the arm that goes down into the box. That strip which hides the internal workings is missing. So dust and crud can fall in.
You can see what gear u are in, D 321 ect.... its the tiny thin strip in the middle thats missing
am sure thats the one!!! will have A SEARCH FOR IT ITS STILL IN THE VAXHALL PACKAGING UNOPEND!!!
Blimey!!

Btw what was that buzzing sound, i mentioned it when i was at yours but forgot

It comes from the underneath the drivers side door really, wheel arch area.
When the car was idling, and you went, P-R-N-D.. you put it into D and it came on quite loud. Did not do it in 3,2,1 just D & R & P.
Give the car a little gas no more than 1k rpm, let it idle again and the sound had gone :-/
Ohh hows your little project going, get it running?