I went ahead and replaced the Cross Contacts with Grabber ATs, and so far, I have been very pleased with the result. The overall ride quality is improved, and they do not seem to transmit the impact of Kent's apalling pot-holes to my lumbar spine quite as much. I checked with my insurers first, and they had no objection to the lower load/speed rating.
Incidentally, when AJS Tyres removed the old Continentals, they found that one was rated 'E' for economy, or eco, or some such word magic, and contained much less rubber than the other three. I can't remember which supplier fitted it, but this is something to be aware of!