Airbus A340 -UC

I have booked flights to Shanghai in September and I believe we will be flying on an Airbus A340. Any time in the past whaen I have travelled to Asia with BA or SIA it has always been on a 747-400. As this is my first time to go with Virgin UC ont this route I was surprised to see it was an A340 and not a 747-400. Has anybody flown this route and what is this aircraft like to fly on - I love the 747 as it always feels like there is loads of space due to the shear size of the aircraft - also as I am travelling with another person what seats would anybody suggest us book in advance?