Ex is alienating me. Suggestions pls

Hello

Parental alienation at work here, and I could really do with some thoughts on how to proceed please, and thanks in advance for any suggestions.

Me and my ex partner split up in 2007, and I had to make the difficult decision to leave. My daughter was 5 at the time, and my son was 2. Despite the initial difficulties, I managed to maintain fairly regular contact picking them up and having them for a few days at a time.
At the start of 2009, I had to move 200 miles away to begin a medical treatment process. The plan always was and still is for this move to be temporary, moving back nearer once treatment is complete. It was when I moved away the problems started, despite my best efforts to see them when I could.

My daughter all of a sudden stopped wanting to talk to me and would give no reason, and my ex would always say in front of her that she doesnt have to explain herself, effectively enabling it to continue, which it did. My son copies her big sister, so he stopped wanting to talk to me too. this went on for around 2 years. I rang several times a week without fail, and did my best to tell them i love them and want things to be better again. My ex would always try to start an argument at any opportunity, and I realised she was doing this deliberately with my daughter in the same room, fakeing crying, and making it sound like i was shouting, being nasty etc. At the first hint of an argument, I used to hang up. i never shouted.

I managed a holiday in 2011 with them for a week, with a friend and her boy. She commented that I have the patience of a saint with kids, and there was a distance between us. I gave them all the love and fun I could give them in the week, but as soon as they got home, their attitude changed, as though being nice to me was not allowed. My ex brought up some trivial thing at their bedtime which really upset the kids, and she somehow managed to get the kids to think i was being really nasty to them, and they started screaming at me to go away and stay out of their lives. i just said i loved them, and glad they had a fun holiday. No point trying to reason with tired grumpy monkeys.

then the silence returned when I called. this went on for 3 months until christmas. I drove 200 miles to take them to toys r us to get presents, and went for a meal. all was good until they returned home, and their attitude changed completely from friendly to complately hostile, and within minutes they were once again shouting horrible things at me, most of which sounded rehearsed, and not what kids would come out with.

I had major surgery start of 2012, and spent 3 months recovering. I went to see them twice after that, both times there was hostility towards me, but i always kept a smile and told them i love them, and want to have fun times.

I worked hard to earn enough to afford a holiday this year, and thankfully it has worked out this time. Its amasing how great everything was out camping with a couple of friends and their kids. Away from their mum, they are top kids, and I do what I can to have as much fun as possible in a set timescale and budget. Last night though, after having a fantastic day with no problems, a phone began to ring at bedtime. My ex had given my daughter a mobile phone. She answered it, and as soon as it disconected, my daughter went into all out rage mode screamed "I F*cking hate you, you are always nasty and mean to me, and im never going to love you again". I tried for 5 mins to calm her down enough to ask what had i ever done that was nasty or mean. The answer is nothing at all, but she refused to answer. At this point, my friend took over and got her calmed down and into bed. Turns out she only knows im being mean and nasty from hearing her mum on the phone to me. Hmmm. Funny that eh?

How do I tell her whats going on?

oh, and she packed a baseball bat with no ball and a real hunting catapult in with my 5year old boys stuff. Now confiscated and binned, but W.TF?? if you went into a shop with this sort of catapult, you can be done for all sorts of things. and a baseball bat without a ball could get someone into serious trouble.

All this since my medical thing started, was fine before that.