Hi Conrad...
I have been with BT for a few years and have found their service excellent - fortunately have not had to use an customer support, so cannot comment on that.
However, they started a while ago creating ridiculous packages/options for the service. I got in early and am uncapped, with 2Mb for a reasonable price. They have offered me upgrades in the past to the upto 8Mb, however the new 'options' were full of junk that I realkly don't want, and costing substantially more. So for now I am sticking with 2Mbps, and have no wish to leave BT due to the excellent service. I am also keeping well clear of the BT-Yahoo side of things!