I regularly fly BA World Traveller between UK & India.
Check-in online at ba.com as this will let you select your seat. Tip - it will only let you check in 24 hours before your flight departure time, so try it at 23:59.
Check out SeatGuru
http://www.seatguru.com/index.php
for the good seats and try to bag them first.
I agree with Paddy - the WT seats are quite comfortable, however you can mitigate the lack of leg room by choosing your seat carefully. I particularly like the "ears" which fold down on the headrest, so that your sleeping head doesn't flop over onto your neighbour's shoulder. The foot rest, in my opinion, is not all that good an idea as when it is down, you can't stretch your legs under the seat in front and when it is up you continually crack your shins against it.
As a comparison, I flew Lufthansa on my last round trip due to the uncertainties at the time about the BA CC strike. I found the cabin service to be better than BA, the seat however, was less comfortable and the IFE dire! (no seat back screens and movies shown on 19" monitors on the ceiling.). No online check in was offered either, so I was stuck with what I was given.