No problems Roy. Everyone is entitled to their own opinion. I too would run Castrol R 10W60 if the car is used regulary on the track, to counteract the thinning of the oil as the oil temp soars. But if the temps are regularly over 130C, I would recommend an oil cooler
As for 10,000ks, the best thing to do is an oil analysis. That way monitoring aspects such as fuel dilution, wear metals and TBN can truely give you an indication of how long an oil can stay in an engine. Again, if the car is track driven, 10,000ks is too much as it would be loaded with soot from blowby and fuel diluents (from rich running).
For a pure street car, 10,000ks on M1 should be no problem.