Last weekend the gold line did not pick up but the BA holiday duty office did and it was all very straightforward. It helps them if you have suggestions ready (that are in line with the rebooking policy at the time of your call), so do think about what your plan B would look like in advance. Of course having a plan B, even if vague, should really be the case for any traveller, regardless of any upcoming weather.
I won't type out the duty office number on here but it will be on your car or hotel voucher that you can get from MMB. You're looking for a London number, dm me if you can't find it.