Are you travelling in ET (economy?) If so, Row 9 is the exit row with about 38" pitch and reclines fully. The aisle seat is probably the best seat on the bus.
Row 8 does not recline. Do not sit further back than row 9 as seat pitch reduces to between 30-31".
BA has flexy- seating on the european runs, meaning that the seats can be converted from 6 across to 5 across by condensing the B seat. The Club (business class) cabin is 5 across, (A,C, D,E,F) and economy is 6 rows across (A, B, C, D, E, F,) EXCEPT for the first row of economy, which is left in the Biz config to stop the attendants bashing your knee with the trolley as they come thro' the curtain.
The risk with taking a seat in the first row is that if more biz class passengers book, BA will move the curtain back a couple of extra rows, and you will get tipped out of your seat and probably end up near the back of the bus in the tight seats.
IT HAS HAPPENED TO ME!!!
Take 9D or 9c and have a good flight.