BA will defend using the Montreal Convention, which means compensation would not be paid for loss of enjoyment. You would be on a hiding to nothing. BA will not roll over on this - they would go to court and likely win if you make any sort of claim along the lines you seem to be taking.

You may have an a case using the Consumer Rights Act 2015, in terms of not getting what you paid for (i.e. a reclining seat, not the legroom) - see the link in the Dashboard for more details.