Tin, in answer to your questions
Looking at the Met Office data for the weather station closest to me, the average high temp for January and February (our coldest months) is 7.9C/46F.
Here is the data, if you want to see other months:
Met Office: averages 1971-2000
When I first started growing orchids, I chose Masdies as they seemed very well suited to windowsill culture here in my house.
As you know, I have expanded what I grow - mostly through the help of OB!! and of course the OB Projects. But I tend to stick to cool/ cold growers as I have a better chance at making them happy.
Interestingly, I seem to have better luck with mottled leaved Paphs than I do with the green strap leaf types. (which seems a bit backwards to me, but I'm not complaining! I love the mottle leaves!)
If you go by USDA Zone equivalent (which has limited use, as it only goes by minimum temp) I would be equivalent to USDA Zone 9 approximately. But that gives no indication of the differences in summer temperatures.
At this moment the ambient conditions are 16C and 97% relative humidity.