If this happens again, check out this thread first and/or ask in this forum.

https://www.flyertalk.com/forum/brit...5-edition.html

To summarise, BA in this circumstance can either offer you an involuntary refund - which unfortunately has to go via Expedia - or rebooking, but you must give BA a chance to do this, usually by calling them. So they may have found a route with IB or TAP to rebook you. If you didn't ask for a rebook then you can still claim the full refund.

For compensation, as opposed to reimbursement, then weather is a valid reason to avoid paying EC261 or the UK equivalent, and there is a dedicated thread on that here:
https://www.flyertalk.com/forum/brit...uk261-apr.html

I best summarise that one too, and your only real chance here is to take the matter to CEDR after 8 weeks and argue on the basis of "all reasonable measures", or the lack of them, if you can demonstrate that other aircraft could land that day, and/or perhaps the response from BA when you rang / DM them. In particular there is a case known as LE v TAP, which may help you.