Thanks for all the advice, it seems that BA aren't liable. I will still arrive at my final destination on time (and the reason for the cancellation was given as weather), so no reason to pursue a EC261.
I think I will pursue AMEX though. I spend an awful lot of my (and employer's !) money with them and had always thought that using their cards would protect me in the event of a 'travel inconvenience' as they term it.
I've already cancelled the hotel booking on line, so not much point reaching out to the hotel. Maybe, I should have offered a free night in the Sofitel to the FT membership rather than cancel it !!
At the end of the day, I'm not really out of pocket as all it means is an extra night at home in Manchester (and an earlier start). I'm just annoyed that I booked such a relatively expensive hotel, but on the other hand, glad I didn't accept their offer of a cut-price upgrade last night !
(CWS, tied up with work until > 1800, so neither of the options you suggested would work for me, thanks anyway)