Thanks for posts, ladies.
OK, developments: ex-dp sent a text to ds's mobile today (sounds ridiculous just writing it - he's THREE!) and then texted me to ask me to help him access it and read it. I read the text to ds, and then replied to ex-dp saying I was unhappy about encouraging ds to use a mobile: he uses my laptop but doesn't have his own; uses the household telly but doesn't have his own - and this is how I think it should be in relation to having his own mobile.
I stressed that ds is welcome to send messages to Dad "through" me on my phone any time he likes, and that ex-dp is at liberty to text/call on my mobile and landline.
Ex-dp has texted back thus: "It was lovely to think I could send him a message personally. Please don't impose your negative views about it on him. It's really important to me and I'd be grateful if you would just go with it."
The problem with me "just going with it" is that I absolutely do not believe it is right, and I would be facilitating something I disagree with - and don't even know to be safe. That isn't bloody fair, is it?!
So what can I do? Although ex-dp has moved out and is on his second skiing holiday in a month , we do - believe it or not - have joint parental responsibility, so I don't have a right to simply not co-operate, do I? Don't we have to reach a compromise? Or, as ds's primary carer, can I not co-operate on the basis that I do not believe it to be in ds's best interests?
Argh. Seems so flipping petty, but there we go - has to be dealt with. Sigh.
Thanks for any thoughts.