What sort of items is he taking? There is no reason why he can''t take personal possessions and agreement can''t be negotiated about sharing household items. If he is taking items without agreement you could consider changing the locks so that access has to be mutually agreed.
He has taken the playstation and some DVDs, which is ok but he said that he was going to leave that for the boys, but he has now changed his mind and wants it in the new place for the boys to play there when they see him at weekends, which I suppose is ok, but as long as he is not going to start taking items that we need each time he comes here.
Be careful, my ex emptied the garage one afternoon when I was out! Take all precautions to prevent him entering. I did not change locks but found other ways e.g chaining and bolting front door and leaving through another door as I knew he didn''t have that key and disabling garage doors from inside.
It sounds like he has taken the kids toys (or was that toy his???) that''s not fair on the children and it sounds like you are unlikely to be able to afford to replace. You need to be a step a head once things go you are unlikely to get them back!!
to be honest the more you try to communicate about this the better.
It is pretty pointless starting a battle for most of this stuff, unless its worth more than £500 not worth fighting anyhow.
It can get petty, but all the stuff will change etc.
I would say, without knowing your background, as long as you have stuff you ''need'' like a washer and a cooker and a bed, thats the main thing, everything else will change.
If he took the playstation, get a wii or a xbox...