Hi Peter.
there is a book The Men Who Flew to Warsaw by L Isemonger
It is part of the African Aviation series no 12 and can be bought at the Aviation Hobbyshop.
Contact karel Zaayman at
karelz@yebo.co.za
and he will organise it for you.
It has the a/c,losses, crews and histories of 31 and 34 sqn.
It is not a complete history but very good.
Stefaan