Road Wheels & Road Wheel Recommendations?

I've got a set and they ride really well, ideally best suited to flater, faster roads. The one niggle I have is they flex a bit when climbing out of the saddle to the point where the rear cage rubs the spokes but if I know I'm likely to be riding over any lumpy stuff I swap to Ksyriums.

This sounds like the wheels moving in the drop-out. Have you considered swapping to better skewers (shimano have the best design).

Difficult to imagine the wheel moving so much near the axle through flex alone. You can also space the rear cassette out up to 1mm. Which could help. Probably better to solve the problem, and not just the sympton though.