I tend to remove him from the situation if he's being naughty - I sit him on the chair, explain to him what the problem is and what he needs to do next time, and then he gets off. But removing him from the situation makes sure I have his attention. If he does it again, we do the same thing but he stays on the chair a bit longer before he can get off.
This sounds like a good approach, I think I might try this starting tomorrow. Can't hurt, right?? Lol.

I know what you mean about him stiffening so you know he's hearing you - he's just choosing not to listen. Mine is the same, I know there is NOTHING wrong with his hearing because he can hear his father's ute coming down the road on his way home from work before I even can, yet when he's 2 metres away from me he acts as though he's totally oblivious to what is coming out of my mouth.

And he's far to bright a child to not be able to understand what I'm trying to tell him, so at his age and stage of development those excuses are no longer holding much water for me either!

my-three-monkeys, I think the holiday period has really upset his routine too actually, he responds so much better to a good routine. When DH is home on weekends, DS1 is a complete terror, so I'm already well aware of what a change in routine does to him. it just seems that he's not improving and usually things only take a day or two to settle down after an upset to our daily lives, so I was just starting to come to a loss as to what to try next.

Well thanks for your tips ladiesl, will give it a go tomorrow!