Well, I got a reply from LTSB. They said that the expired certificate should have been accepted and gave a link to their help pages on how to check certificates. The example given is clearly a LTSB cert but the expired one certainly was not.
I've replied and told them that was really bad advise from a bank!
They did not tell me why my transactions were being linked to another non LTSB site so I've asked about that again too. I do know why of course - it's for marketing stats but it's another risk with respect to security.
I might continue to stir it with them, if e-mails don't give good/honest answers, it'll be a letter next!
Terry.