roncerr - Sorry for the delay, I've been away from the screen for a bit.
I think you may have something in it being the page complexity. After experimenting, I have realised that the excessive delay does not happen with all pages, just those that I spend most time on, and they happen to be newspaper/magazine front pages.
I'm surprised that a modern pc with all this processing power gets slowed down so much by even a complex website page (how complex can they be for goodness sake!), but there you go.
Many thanks for your insight.