John, studying this video from a car roadholding point of view your car seems really 'oversteery'. I know your speeds are very high and you have lots of power but the back seems to step out of line even with the power off.
When I was doing my trackdays my car was quite neutral and if I got things wrong i.e. entered a corner too fast it would understeer or four-wheel drift to the outside of the track. I honestly can't remember having oversteer. If I was drifting and missing the apex I could lift a little just to bring the front tighter but it wouldn't get the back to come around. It was very safe in that respect and like you say these cars are great handling cars - they want to help you out!
Your video at 4.55 when you are at Copse, you tighten your entry a little and the back comes around really fast. If you spectate there during a race the people who get brave and enter too fast end up on the tarmac over the kerb on the outside they very rarely oversteer. At 7.25 you end up by the outside kerb but again it's the back-end that starts it. I'd be interested to hear what Matt (racer) thinks about your 'set-up' he knows the car better than me.
Are your rear tyres the same type as your fronts and what about rear stiffness? Perhaps it's a bit stiff? Tyre pressures?
When you took me around Spa your car behaved differently than this - the only issue seemed to be the rear becoming a little 'lose' under severe braking when the nose was pinned to the ground i.e. into the esses before the pits, or into the first hairpin.
It's a very entertaining video, I really enjoyed it and you were good at 'catching it' with the opposite lock. I also am not underestimating your speeds, the G forces must have been really high - I can see something swinging under the dash that shows the cornering forces.
Jason Plato makes it look easy:
https://youtu.be/DxJqzLLooko?t=8