Sand and cement in the cold !

Took on a job for family knowing damn well it's too cold really!

Friday I had the back of the 2 storey extension on and ruled off by 10am. It didn't rub up until 11pm under lights (FML)

I've been chucking a bit of rapid set in and lots of hydrated lime. Is there another trick I'm missing to get the b*****d stuff to set quicker ?!

All advice welcome !