Hi blaireau ...
Could you please check that fuselage serial number reference again (WL540) as I don't believe there was a "WL" allocated to an RAF Chipmunk ? Also checking my records ... a 540 numeric allocation also doesn't seem to have been allocated to a Chipmunk ? There are a few odd serial allocations recorded against the UK Military Chipmunk production run ... so I'd be very interested to know if we have something new here.
Best regards ...
Coff.