Thanks for the reply, KVS. I'm really keen to get this working (esp as I've paid for Diamond for two months!) but I don't have anything like that sort of smooth experience so far. My internet connection is 8Mbps ADSL and I can easily stream BBC iPlayer HD streams, as well as quickly browse websites.

I tried some testing - here were my timings:

Checking for EDI-EWR *A award availability in May:
SNT: Awards/StarAlliance - initial search 1m50s; clicked 1 day forward - 1m24s
ITA: Awards/AC-StarAlliance - initial search 0m44s; clicked 1 day forward - 0m34s.
ANA website (timing from clicking the 'flight search' button once logged in) - initial search 0m10s; one day forward 0m18s

Any suggestions on how to improve matters would be much appreciated!