On a recent long haul flight my seat in F would not recline (12 hour flight).
The flight was full in both F and CW so I could not downgrade and still get a flat bed.
I am sorry to hear this, but unfortunately it highlights our need for the decision to re-fit our aircraft with more premium seating.
A seat reclining mechanism can fail at any time and usually a member of staff travelling on duty can be asked to swap seats. The trouble is, with the airline's success in selling "F" and "J" seats, staff on duty now tend to be in WT or WT+ if fortunate!
I think, in your shoes, I would take the GBP1000 cash option as any mileage will just add to your stockpile!