The A340 is one of the older planes that Virgin flies on that route. I recently had a 787 be swapped for an A330, but so far have never had an A340 be swapped for something else, but that might just be my luck. I find the A340 seats a bit wider than the 787 or A330, but that might just be my imagination. The A340 seats are in desperate need of TLC, they are old with a lot of wear and tear that shows. My flight a few weeks ago had a tray table that didn't pop out of the slot, the FA had to manually pull it out using a knife.
It's a fun plane to fly on once or twice, the 4 engine planes are rare these days and an experience when taking off and landing.