So I have 50 high density concrete blocks left over from raising my garage floor so it is flush with the car and bike lift platforms which the local builders merchant will refund the cost of if I take them back. 50 at 19 kg each is 950 kg / 2094 lb, just shy of a ton.
Handbook says max rear axle weight is 1840 kg / 4056 lb. The EEC defined kerb weight with full fuel tank and 75 kg / 12 stone (near enough) driver is 2100 kg / 4629 lb gross with 1000 kg / 2204 lb on the rear axle.
By my maths that implies I can load 840 kg / 1852 lb in the back. Probably a bit more as the tank is down to 1/4 full and I'm 10 stone dripping wet at most.
Looks like 46 in the back and 4 in the passenger footwell will do it.
Only 2 miles down a twisty hill but its still seems a scary load for a passenger car. The £75 refund on my flexible friend will be nice but I'm not inclined to risk popping the airbags. Cleaning out all the dust afterwards is quite bad enough a prospect thank you (quietly ignoring the slog of manually loading and unloading).