Take the A380 over the B777 and try and get on the upper deck as it's much quieter. Avoid the T7 in 10 across configuration and avoid the B787 in 9 across if you can as they are like sardine cans. QATAR T7s are 9 across and very comfortable, however new deliveries will be 10 across and they use the B787 on JNB in the 9 across config.
Have a look at Turkish Airlines as well, they are showing some cheap fares, though you may have to suffer a narrow body between the UK and Istanbul.