Having had a blowout at 70 mph in the IS on the M25 the car behaved as it should of...no dramas, held a straight line and slowed down pulling over to the h/shoulder, the reason cars crash after a b/out is people panic and do the wrong thing i.e brake!! a big no no at 70mph thats what will throw you towards the central reservation or flip you over into a roll.
Im not saying what your doing is wrong, be happy that you have found a place that will help you find a solution to your problem.....LOC and WIM, it will be impossible to reach every IS owner.
Good luck