I had a response from Fox:
Thank you for your email.
From 1st March 2016 FOX will no longer be available on BT. Viewers can continue to enjoy their favourite FOX programmes including brand new episodes of The Walking Dead, and UK premieres of NCIS and American Dad! on Sky 124, Virgin 157, TalkTalk 422 and Now TV.
For full information on how to watch FOX please follow the below link:
It seems available on all platforms apart from BT.
I wasn't offered any discount when I called yesterday, just given the sales pitch of how great the other channels are etc etc. So I asked to be released from my contract early which was done without any question.
No need to wait for the email - I didn't have one when I rang yesterday. I just started the conversation by saying I've heard Fox was being removed on 1st March and went from there.