[Solved] Crazy repeated accusations. (long story)

Hi, first time I've braved it on public forums regarding this. I hope someone finds the time to read it an offer any advise.

Ok, roll back a year and a half. I come home from work to find that my wife has left and taken the two children (4 and 1 year old) with her.
I call and ask where they are (as I was home for hours thinking they had just popped out) and basically get thrown a bunch of frankly bizarre accusations, which after trying to get her to see sense for what seemed like ages,
Things like.
The week prior.. daughter was found (by me) at the end of her bed, lying sideways across it. I called out to mother to come and look (it was quite amusing at the time). She didnt. I had shower. She came up afterwards and saw her and noticed her bed was wet and stank "of fish" her underwear was dry.
Here takeaway from this was that since it could not be explained, I must have some something. It was never actually stated what it was i was supposed to have done. but either way it made no sense.

There were other claims as well as apparently my daughter is purported to say that "daddy tickles me down there when drying me after a bath" now take in to account that I have never actually bathed my kids on my own. it is always with the mother present.

a bunch of other random things were brought up. I was investigated by the police, daughter was questioned about 3 times (ex wasnt happy about how it took place the first 1 or 2 times apparently)
anyway, the police spoke to me over the phone and asked me about the claims and at the end of the call said that they would not be taking it any further.

Then she took me to court to try to stop me seeing my kids. By the time I saw my kids again it was for a 40 min session with CAFCASS , SIX months after last seeing them.
I saw them again in a similar fashion a month later.
Next time was at court, the judge said that I should have access at a contact centre every few weeks until the final hearing which was scheduled for February.
Come Feb, there was a 2 day hearing where the judge heard all the statements and we had to both take the stand and be questioned. The mother blatantly lied on under oath (as did her sister and brother in law who were called as "witnesses") saying that she had never thought about accusing her own father of abusing her. This is untrue. Let me back up a few years.
The ex has some SERIOUS mistrusting men issues. About 3 of her friends have all accused their own fathers of abusing them or have at least had doubts about them. A few years before first child was born, the ex was going to confront her own father because she "didn't know if he had abused her"... she had doubts... she couldn't remember... so she automatically come to the conclusion that it must have happened... she remembers him waving a watch in front of her as a child... trying to hypnotize her in a comedy pretend stage hypnosis way. Anyway, her sister and myself managed to persuade her to see sense and not do anything about it as there was obviously nothing in it.
She is the sort of person who reads these books like "A child called IT" and those kind of books about child abuse.

Anyway, the judge at some point asked for her to undergo a psych evaluation because of her history with eating disorders/depression/suicide and suchlike. The outcome was that she suffers from what is described as having "Overvalued Ideas". Which apparently isn't a mental problem. Although if you read about it it seems that it is quite a big deal and explains EVERYTHING. The report said that she should continue (she used to have therapy for it about 10 years ago but she moved and never continued) a course of Cognitive Behavioral Therapy sessions to get through it. This has been ignored by her and the judge despite bringing it up a number of times.

Back to the final hearing. at the end of the 2 days, the judge basically said that for all of the accusations, it wasn't a case of "on the balance of probability that something had not happened" , he said that there was nothing at all in any of the claims and that the ex should not believe everything that children say as gospel and to add 2+2 to come up with 7.

So, this was a year ago now. and I have just had the 2nd overnight contact session. Before now it has been about 4 months of seeing them for a few hours/saturday every couple of weeks. Before that it was contact centre, and meeting at playcentres. All of which was agreed by the judge solely to placate the mothers anxiety.

I'm missing out quite a substantial amount of details here .. its been a verrrrrrry long 18 months and just when I think things are starting to get back on track, something happens yesterday.

The ex calls me a few hours after picking the kids back up after them staying at the weekend. Wants to meet. I agree, we meet, she comes out with a outlandish claim that apparently my son now 2.5 years old) has a scratch on his hand and that my daughter has said (she is now just turned 6) that MY mother scratched it on him as some kind of punishment?! Apparently I was there and said for my mother to stop, but she didn't. and apparently went to scratch his head and told him that she hates him. absolutely untrue and very weird claim to believe.
Now it should be known that ex and my mother never really got on and this follows on from apparently a few weeks ago my daughter told her mother that my mum had told her that her mummy is a "bad mummy" and a "naughty mummy" this is also completely untrue. All of these are met to my argument of why the heck would me or my mother compromise the process of seeing the children after spending sooooo much time and money fighting the outrageous claims from before?!?! it makes no sense.

Anyway, this is where i am at as of today. Still waiting to hear from solicitors to find out what options are, but I fear that there isn't much which can be done.
I'm at the end of my tether with all this now. The conversation yesterday with the ex brought back memories of the exact same conversation 18 months ago, trying to get her to see sense and that it makes no logically sense to think something like this has happened. An argument which I cannot win as.

Thank you for reading. I will answer any questions which are relevant if it helps to give advice.

Cheers