There is lots of background to this (7 years worth [rolleyes]) but I will try and keep it to the bare bones and avoid drip feeding.
DD is 9. Her father walked out on us when she was 2, and has made very little effort to stay involved in her life since then. He refuses to speak to me (he's a bit strange like that - he has 3 DC by 3 women and won't speak to any of the mothers 
)
After years of difficulties, we have come to the current situation, which is that I arrange by text and email with his parents (who he lives with) when DD will visit them. As I now live about 100 miles from them, I take DD to my parents house which is about halfway, and the GPs collect her from there. This has been working fine for the last couple of years.
For this half term, I asked his parents a month in advance if they would like DD to visit and explained that it could be for no more than 4 days as I had some things I wanted to do with her as well. They sent a reply saying "Yes great, our car is in the garage on 24th so how is sat 20th to tue 23rd" to which I agreed. I've heard no more since then apart from to confirm collection time.
They came to collect her from my parent's yesterday, and GM asked my mum (I'd had to go before they arrived) if DD could stay an extra couple of nights as they didn't feel they were having her for long enough and that it wasn't really 4 days when you took travelling time into consideration. My mum said it wasn't up to her and told them to talk to me about it. I then get a text from GF saying "[EX] want's to discuss [DD's] visit with you, please can you ring him about it"
I sent a message back pointing out that I can't ring Ex as he refuses to give me his mobile number and that I wasn't prepared to change the days now as it was too short notice. Since then I have had 4 texts from GF's phone, firstly asking me to ring on that number (why the fuck could he not just ring me then??), followed by three messages giving me DD's father's number and repeating the request that I ring him.
I think this is Not On for several reasons - DD is going for the days that THEY ASKED FOR for a start, and if Ex wants to be involved in the arrangements he should do so when they are being bloody well made. I refuse to be drawn into discussion about extra days at this stage. He also can bugger off texting demands that I ring him. He can ring me himself if he suddenly feels the need to get involved. That's not unreasonable, right?