Mew Gull
Sorry, I only saw this thread rather late in the day. If it is of interest, Lesley Hunt's book 'Veteran and Vintage Aircraft - Enlarged Edition' of about 1968 (I think - no publication date is shown) records XF at Wycombe Air Park (sic) as follows, in a list including a Monospar, 2 x Rapides, 2 x MS 230, Stampe, Fokker E3 replica, Antoinette replica, Piper Cub, Proctor and Nipper (Dixon):
"Douglas Bianchi's Personal Plane Services offer: ........Mew Gull G-AEXF ex ZS-ASM, winner 1938 and 1955 King's Cup races and holder UK-Cape and back solo records 1939 - now HAPS machine....)" There is also a small photo of XF airborne but with no attribution or further details.
Kenneth Munson's book 'British Aircraft' (Ian Allan) of 1963 lists XF as owned by JEG Appleyard. No photos or other info.