I suspect that Overload's suggested inbound route BARIX-NUMPO would be likely to aim the "boom" towards the South Wales coast. Whilst I don't have a problem with that, I don't think it would find "a welcome in the hillside". Of course, the option of slowing to subsonic speeds a bit earlier to mitigate the perceived problem might be acceptable if it meant that Concorde was able to maintain its optimum subsonic level/speed until closer in.