Dougie, I've had the same thoughts when I've spun my Spitfire while racing, I should be able to catch this. Sometimes I do, sometimes I don't. A racecar usually has a much stiffer suspension and once you cross the limit, even though it's a higher limit, you're a passenger in for the ride.
My car, while way down in horsepower from the Aston, is a smilier configuration. There's a lot of weight in the front and not much in back with skinny tires. Once the back end starts to come around you have a very small time window to get it back in shape.
The side forces (slip angle) start to build up while the weight comes off the back end and transfers to the front further reducing the grip at the back. Hitting the brakes or an abrupt gas pedal lift, puts more weight on the front and makes it worse. Once you hit the grass, especially heading backwards, all bets are off, there just isn't enough bite to allow the tires to do their job. Recovery is easier in a car with 50/50 weight distribution (spun them too) but in a LBC it's different.
It looks like the walls are very close at Spa, much like Watkins Glen. There's just enough room to parallel park if you can pull off in a controlled manor, no real room for spin recovery.
I'm just wondering how much it's going to cost to fix the thing. It looked like the rear quarter is a bolt on part, not welded so it may be easier from a labor point of view but I'm guessing not cheap.
mike