Brilliant, thank you for that 134brat! The occasion wasn't the first flight but the first rollout, which occurred on 15th April 1962. That means that next to APPS, APPR, AOZE and APTE were also in the UK at that time. Considering that there may have been bit of preparation involved in reregistering the aircraft and preparing them for shipment (assuming they didn't fly there), APPS or APTE could be the most likely candidates.
From the photo I found on ABPIC, at least APPS carried the correct scheme. I'll have to have a look around for photos of APTE to see if this carried the same scheme.