I cant see it being a BA problem unfortunately and very much doubt any knock on costs will be considered in lieu of this. Its certainly out of their control and they have done as much as they can most probably in getting you back into London the same day. Its an insurance issue I would think , the cost of the cab either way wont be exorbitant, Ba may pay for some of it, maybe not - I would just pony up the cost, put it down as one of those things and look at in the cold light tomorrow..

I wish you all the best on your journey and hope you will be tucked up in bed before midnight with a cuppa. Godspeed.