Thanks for the replies, I shall see if I can get the humidity up.
I grew hybrid F1 cucumbers ( I forget the name ) in exactly
the same conditions last year and was awash with cucumbers.
I only changed variety so I could get viable seed from one or
two of the crop ( the two cucumbers from my hybrid variety that
produced proper seed last year let me down as these would
not germinate ) - I'm tight-fisted you see!

Andy