Thanks guys - I'm building a test sheet to effectively break down all the possibilities, will report back here when all tests completed.
In answer to your questions SEOMike, no flash or Java, not dynamically generated, all the pages load slowly, and I haven't tried disabling scripts yet.
Two of my concerns were the server and the location of the server. The audience is UK based, but server is on West Coast of the US. I've tested on different servers (in UK and US) now and the loading is fairly similar. So those things ruled out.
I've still got four javasrcipt files being called from the top of the page, and a design which includes both tables and divs. Going to sort these things out next and see what effect is.
Likewise, will get my images called from somewhere else to set up more connections.
Thanks so far for your help everyone.