Hello Ian,
I dont have the Pye record unfortunately but the covers can be found quite easily online. There is no information about the recording sessions on them however. I contacted my friend David Patmore who runs CRQ Editions. He has a huge knowledge of discographies. He doesnt have access to the LP at present either but reckons that Snashall did indeed produce and Bob Auger was likely the engineer. As to location, well it could have been anywhere! David remembers when the record was issued notices were actually very good. Del Mar was indeed a very fine conductor of Delius.
Hopefully more will come to light before too long.