I've just spoken to the Station Supervisors at Manor House and Turnpike Lane, they say they are expecting to remain open this evening until close of traffic, but then will 'almost definitely' be closed all day tomorrow.
The Piccadilly Line service will no doubt reduce throughout this evening and it will probably be closed tomorrow; if there are any trains they will be very few and far between. My advice is check before you travel on the links Hugh has very kindly added, or alternatively on BBCi.
I will add updates where I can although I'm not on duty until 3pm tomorrow, by which time most of you will probably have already made it to work/school/college/etc.
Sorry Glyn, I was off duty when you posted last night. I can tell you Turnpike is open this evening with trains at present about fifteen minutes apart, stopping at Finsbury Park.
On the Piccadilly Line, you can currently go eastbound from Kings Cross, stopping at Finsbury Park, Turnpike Lane, Arnos Grove and then all stations to Cockfosters. You can travel in the opposite direction too, but you must alight at Finsbury Park and catch the Victoria Line to Kings Cross. Line Managers are expecting a good service in the morning (pending signal failures, etc.).