Hi Scott,
Many thanks for your advice. I qualified originally as a VCP in 3.5 (Install, Configure), then requalified on 5.0 after taking 5.0 "what's new" course.
As I have been using vSphere 4 continually for the last 2 years, and need to get the VCAP cert., I hoped it would be possible to do the VCAP exam, having gained the latest VCP qualification...