To summarise the evidence so far:-
Its got skids not wheels (Goodbye Wasp or Skeeter but Scout?)
Piston engine (Goodbye Scout)
A tailboom shorter than a Scout/ Wasp
Very slow
Cab like a Scout/ Wasp
Straight sides like a van
?????
Its the piston sound that gets me. Without it it sounds like a Scout (a lot about) or even an Allouette II
Square van = Dragonfly but none on the CAA register.
Must be Russian if not a Scout.
NB, I see G-INFO has been updated and reformatted on the CAA website.