Flatus
Agree with your thoughts on defending Blighty but if that were the only driver, a decent UKADGE/SAM set up would go a long way toward meeting the requirement. I know the arguments about man-in-the-loop but that and arguing the value of a BVRAAM must be mutually exclusive.
The most likely use of AD Typhoon would be to deploy to wherever next conflict arising to cruise around well above all realistic MEZs, achieving little more than a political presence.
N Joe