I'm not sure that my last post on here should be marked as a "solution".
I contacted BT Technical Support via chat again this morning to ask for an update. I was taken through all the usual suggestions of checking my settings on outlook etc. - lots of stock suggestions clearly copied from pre-prepared scripts. After an hour, I asked to be passed to a manager, who told me there was no record of my chat from Friday where they stated that there was a problem with pop3 their end.
After nearly another hour, he referred the problem to their higher level email team and said it would be resolved in the next 3 -5 days. He assured me that this time there was a record of my chat on my account.
During the course of the nearly two-hour chat, I received an email (via IMAP not POP!) saying that they had logged my "complaint". I hadn't actually complained! A few minutes later, I received another email saying that, if they didn't hear back from me in the next 7 days, they would consider the complaint resolved. After finishing my chat with the manager, I received yet another email with a link to track my fault. When I click on the link, it says that there is no account attached to my BT ID, which is rubbish. I tried clicking the link in an incognito window, and it took me to my account, and a page saying that the tracking service was not available at the moment!
