Putting a blanket policy in place would make little sense for BA (why give passengers flexibility on routes that are not being significantly disrupted?). The weather for Heathrow isn't forecast to be too bad. Wind is forecast to be pretty much straight down the runway for much of the day, so limited crosswind component. Some stronger gusts. Arrivals are regulated so there will be some delays and likely some cancellations, but BA will probably target cancellations on routes where they can accommodate disrupted passengers on alternative flights.
Completely agree that this is the way BA thinks but there is an argument that allowing people who don't fancy traveling anymore to take a refund and clear off is actually in BA's interests. Delays mean there is a fair chance that inbounds will be disrupted, leading to people missing connecting flights. Opening up seats on those for these people to sit in avoids the cost of putting them in hotels for potentially a few days until a seat opens up. BA absolutely does not work this way though - if you compare their approach to travel waivers to any of the big American carriers, you'll see a huge difference.