Thanks for the comments you’ve given so far. Right now the consensus is split between ‘move host, stick with Movable Type’, and ‘stick with host, move to WordPress’. Because I have limited time this weekend I will stick with WordPress for the next few days, as it will also allow me to try it out. I’m quite liking the theme that I’ve found (and may see about adopting a similar one should I switch back to MT) and the whole application feels very snappy and clean; however, I have yet to import 4000 entries and 6000 comments so we’ll see how it stacks up after that. But from what I have seen so far it’s a world away from the versions of WordPress that I tried 2 1/2 years ago and disliked.
As for the performance issue, I first had an email from my host last night and have responded today – we’ll see what the response is. I’m primarily interested to see if it really is Movable Type that is causing the high CPU usage (I imagine it is but it could be something else less important), and whether shutting it off has made any kind of difference.
If you have any further comments about what I should do,. I will read and consider all opinions.