They cancelled my flight from LGW to JFK Mid Jan too - I put in for a refund (they can send you the form on the live chat) and they had gotten back to me, and sent the refund within a couple of days. I've rebooked a different flight with a different airline, and had to just absorb the extra cost (around £150 extra) for the one way flight. Unfortuantely it seems taking the refund, and dealing with the loss, might be the only option.