Answer to the question is as follows (courtesy of PeterNem's scales
):
Wheel = 14.7Kg
Rear door cards (pair) = 2.5Kg
Rear seat backs (pair) = 14.7Kg
Rear seat base = 5.2Kg
Rear seat side bolsters (pair) = 1.4Kg
Bonnet inner lining = 0.6Kg
All the rubber sound insulation (mostly from the boot under various carpets) = 12.3Kg
Boot carpet (floor) = 3.8Kg
Boot carpet (sides) = 1.2Kg
Rear speakers = 2Kg
Jack = 1.7Kg
Various plastics from the boot, sills = 2.2Kg
So
62.3Kg! There are a few more bits and pieces that I've taken out not in the pic but nothing of substantial weight.
More needs to come out though - headlining I think will be next and need to have a nose behind the dash for more bits to come out. Passenger seat will probably come out for the next track day, and I think the carpets will go too.
Book weight is 1,240Kg, add the sunroof (20Kg) and the stuff on the lawn means my car should be roughly 1,200Kg. Will look for a weighbridge to confirm that.