JammedStab pointed up the clip at 4:35; the same clip is glimpsed at 0:42.
I had about two years as a very undistinguished Vulcan captain some forty years ago. The brain is going, of course, but I just do not remember taking off or rolling with the airbrakes out. It seems now to have been quite unreasonable (bad airmanship, plain untidy) to do so. The clips will have been taken from some sort of test or display sequence.
The airbrakes had a puny effect at circuit speeds although, as PN says, on a balanced approach their use allowed a higher engine setting where the engines would be more responsive. Moreover the direct drag that they generated slightly reshaped the drag curve, so that the speed at which you could find yourself behind the curve was a smidgeon lower.
On an ordinary takeoff there was absolutely no reason to have the airbrakes out – they would just generate drag to oppose the huge thrust we always used to escape the surly bonds. That would not matter much except that there must be some sort of risk that we would leave them out for rest of the trip. What was good for the takeoff was good for the roller; it only took the flick of a switch to bring the airbrakes in as you brought up the power.