Croydon 'Diversions'
There were plenty of Airfields local to Croydon including Kenley and Biggin Hill plus the odd landing ground along the railway from the Kent coast.
However Croydon did suffer from local fog rather than low cloud. Of course its advantage was the road and rail connection to London which was important at the time.
I can remember when Banstead Station had its name on the roof for use in the early days of radio, and the Croydon revolving searchlight beacon was kept going for several years after the airfield closed to commercial traffic.
Gatwick only became popular when flying developed for overseas holidays, and only then when it got a hard runway as the location was noted for getting waterlogged before.
In fact Redhill would have been a better option as is was lower and on the railway line plus had good rail connections to London, also could have been extended which Croydon could not.