Personally I think the vast majority of BA seats are very comfortable, have been towards the back on both the 319 and 320 and found both very accecptable, Im 6'2'' by the way, so unless u are significantly taller you wont have a problem.
Do watch out for middle seats, some are quite narrow, as they are ';variable geometry' ie 5 of the six are wider than usual so J class is more spacious. DO NOT get stuck in the middle seat(usually B, I think) its a dog, other than that, have a great flight!