Sammy,
I have a Den phal type (NOID) which is spiking now- I live in South London too so have the same weather as you
My Phals are not spiking though, which I suspect is because mainly they have just finished flowering. After keeping blooming for 8 months in one case, I think I'll give them some more time before they produce more! But you never know with these things... I have an Epicat plicaboa Dancing Queen which seems to have the beginning of a spike in its latest pbulb too- but I think this orchid is a little on the seasonally confused spectrum.
Kay
x