In theory, all guest relations should be able to do it, but it is not something they are used to doing. If one says they can't I would suggest trying another until somebody sorts it for you. I asked at DTD guest relations and they said they didn't think they could upgrade UK only passes or discounted tickets as they wouldn't be on their computer system. They tried and the computerised till did recognise the passes and I was able to upgrade them. I couldn't tell you what credit I received for them because I got a Disney club discount as well and it was all a bit complicated as I didn't see a breakdown of the figures. I was just glad that they were able to do it. I think I saved about £35 - £40 over the cost of 2 x 10 day passes, plus parking, convenience and discount benefits. It was worth it but I don't think I got anywhere near full credit for the 10 day pass which I hadn't used at all. I would ask how much they are allowing against a PAP before deciding to upgrade.