All bmi aircraft are to be fitted with leather seats, it would appear. I was on G-MIDW today (the A320 which is still in the old Star Alliance colours) and the Recaro seats have already been recovered with a dark blue leather in place of the bright blue cloth.
According to the FSM, all aircraft are to get leather seats...not because passengers prefer them, you understand, but because they are cheaper to clean. Personally, I preferred the cloth seats and the shade of blue contributed to the nice, bright and clean cabin appearance. But BA board people are always banging on about superior leather seats so I'm sure this will be viewed as an improvement
Not sure if the change applies to Regional.