Is it normal for one arm to move more than the other?

And are the three holes in the braze on to allow rough adjustment of spring tension or have I misunderstood?

You’d generally have the spring set in the middle hole (both sides). There should be an adjustment screw on each arm to balance the tension (unless they are really horrible cheap v-brakes)

That’s what I thought, however I’ve got the tension screw right down on one side. Might have to disassemble and make sure I’ve not done something daft.

They’re Tektros so not the cheapest of the cheap.

You can also carefully bend the springs to adjust the tension.

If the tension screw doesn’t offer enough adjustment to get the arms moving symmetrically, I have previously bent the springs gently to make them balance…

Take apart and grease up, if still an issue, use the higher tension hole on the side where you have the adjuster right in and see if that helps equalise things.

They’ll often be a little asymmetrical when at rest, not least because one of them’s got the cable outer anchored to it, which will affect the balance. As long as the pads contact the rim at the same time and you’ve got enough clearance both sides, it’s fine.