Many thanks for the assistance! Presently, I've ascertained that there are at least six aircraft still airworthy in the UK/Europe, potentially seven with N1250Y. G-APPL, the Prentice which took part (not G-AOLK as I previously thought) has also been airworthy as recently as last year. It made it as far as the south of France before retiring.
Auster AOP.9 G-AXRR/XR241
Rollason Condor G-AXGS
Beagle Pup 150 G-AXMX
Piper PA.28 Cherokee Arrow G-AWBC
Piper PA.24 Comanche G-ATNV
Cessna 180 G-ASIT
Pulse01 - I'd love for AXGS to be in attendance - I'm looking to gather aircraft irrespective of how far they progressed, plus I'm curious to see what a Rollason Condor looks like with a slipper tank fitted! If you drop me an email martin(at)threshold.aero, it'd be great to discuss you attending.
If anyone would be interested in seeing my spreadsheet thus far, I've still not been able to find a way of sharing it either as an image or a link, but I'd be happy to email it to people should they let me know at the above address.
Many thanks,
Martin