Thanks for the response. As I said elsewhere, I had looked at that page and found it confusing. It also seems to be more restrictive than the hosting I already have, but the main issue I see is that it only offers a choice between Hong Kong or US West, and most of my traffic is European.
What I was trying to establish here was some kind of general guidelines to help me (and anyone else who might be interested) judge when a move to cloud hosting would be appropriate. I don’t seem to be the only one confused by the whole issue.