I spoke with Alan yesterday and it turns out that the robo-voice was his voicemail. Apparently BT upgraded their software or something and managed to delete his custom voicemail message and replace it with the robo-voice. He was muttering about demanding BT pay him 25 quid to replace the custom recording they binned.

At the time I phoned he was out walking. We've both gotten seriously into exercise, walking being one of the easiest and cheapest ways to do that. I however, have my home phone set to forward calls to my cell phone if the landline is busy or unanswered. If the cell call doesn't get answered, then it drops to voicemail. Much more convenient, I think.