Ellie, just a thought, but when you have tried ignoring the behaviour, have you explained to him at the time that's what you are doing? I say to DS something like "Jack, you mustn't do (insert appropriate words). Mummy will pick you up and give you a cuddle when you stop doing (whatever it is)". Then he usually stops pretty quickly and comes up fora cuddle. Then I praise him for stopping the behaviour. It does work for me but then DS isn't quite 2 yet so I think we haven't hit the worst of the terrible twos.

I also find DS is more likely to be naughty when I'm feeding Thomas (nearly 12 weeks) so his new sister could be part of the issue. I just try to spend as much one on one time as I can with Jack while Tom is asleep. Then when Jack wants something while I'm feeding, I say "Jack, you had plenty of Mummy's time while Tom was asleep, now it's Tom turn". Also I often sit next to Jack and read a story to him while I'm feeding. Again, it works really well so far but I'm realistic that it might get worse.

Best of luck.