Phone the docs this morning, they have a fairly new system at the moment where some days doctors have sessions which can be booked in advance and other days they're only available if you phone on the day. My doctor has one of the latter on Monday, so I'm going to ring then and try and make an appointment, and one of the former on Thursday which I've already booked and will cancel if I do manage to find a slot on Monday. I think it's fairly clear it was a mistake to stop taking the ADs, and one I'd best fix ASAP.
(Nationwide told me to talk to HSBC before they would do a proper check on the two credits, HSBC say all is normal and only one payment has been made, I've thrown the ball back in Nationwide's court but I'm not going to spend too much time chasing it. I've done my best to make sure I'm not accidentally stealing money from either of them, and I think it's their problem now)