Raynoil were the cartographers who produced Imperial Airways' charts through the 1930s, and did some maps like this one aimed at the retail market as well. Two shillings would be about £5 nowadays.
1939 | 1861 | Flight Archive
Mrs WHBM
sends her greetings, but regarding your kind offer wishes it to be known that the house has quite enough old air timetables in boxes all around, without getting into maps as well !