saskew

We have just received an email to say our flight from YVR to LHR on 27th March 2019 has been cancelled. We'd booked two seats in CW with an Amex 2for1.

Before I call BA I'd just like to understand our options. I've checked availability and the only reward seats out of YYC in March are 31st (too late), so am looking at alternative airports. YVR only has economy reward seats that week, so I'm looking further afield to SEA which has two reward available in First on 28th March which we could stretch to.

Please can someone refresh me on the rule of rebooking a different airport at no additional cost, does it have to be within a certain number of miles?

Given the flight has been cancelled do BA have any obligation to get us to another airport?

Thanks in advance