I've just tried setting up a free VPN with VPNBOOK.COM (whose servers are in Romania!
)
This utterly fixed the problem - the PC connected via the VPN was loading web pages quickly and without problem, meanwhile a 2nd PC that was connected in the usual manner was only partly displaying the Google logo before eventually timing out.
I have no idea as to the security of the VPN, so I've switched it back off again (Kitz forum wouldn't let me in using it, it said I was trying to spam!)
However, the good news is it might now be fixed - since rebooting and disabling the VPN, I can access web pages without problem so far....
[EDIT : Spoke too soon. The BBC site
is working well now (was abysmal earlier) but other sites selected at random are slow or failing to load or working as normal.
Loading same site via VPN PC works fine though, so it's nowt to do with the modem or phone line!]
Ian