are tomatoes taking longer to ripen this year

I think I know what the probelem here is 

At the plot the toms are ripening nicely and we have had several good pickings of small and regualr size varieties (not beefsteaks yet) The door to the mini polytunnel stays closed to avoid ransacking squirrels etc

At home, in the greenhouse (same size space, same varieties from same seed sources) there are fewer toms per truss and none full size yet let alone ripening. Door stays open so it doesn't get too hot.

S0 .... Keep the door closed to raise the heat (not rocket science, I know but it has only occurred to me this morning) 

I have lots of green toms on all,  but only one starting to turn red, I am sure it is because of the cold nights.