Crewmeal,
When they did the runway extension they added extra fillets to slightly widen the area end of old runway 33 and its wider at S too, but no change 15 end.
However its the extra wheelbase of the 346 thats the issue. The 77W wheelbase is less than a 346, and the sliding of the 77W was not due to the narrowness, so it was claimed.
To be fair we have had dozens (77W) turn in the same area in extreme iceing and heavy rain without an issue, and don't forget we had a Dash and a 737 off the taxiway so it was probably more a pilot error.
However on watching the video of the EK A380 we had it did look pretty tight..yet meets CAA regulations and the NATS A380 BHX taxiing maps loaded would suggest things are wide enough...