I'm happy to let people move units that they forgot to move, or fiddle with a unit's movement as much as they want, provided it's clear they've got spare movement to burn and there's no way they'll accidentally over reach on their movement. And I've only ever once disputed a guy's move of a unit, but that was only after he'd already been very generous in moving units the previous turn, and then disputed a move from one of my units.
Basically Warhammer is a fiddly game, and when we get really strict over minutia like movement then the game can get to be more about fine details than about clever ideas and runs of good and bad dice.
Tournaments, of course, are a little different, as plenty of people really are there to win. I normally play that by ear, trying to act like my opponent does. Doesn't always work of course, like the example above (which was in 40K, but the principle is the same).