Sigh
First lockdown in March, exH texted to say he wouldn't be able to have the DCs for weekends during lockdown as he lives with exMIL and she has underlying health conditions and is anxious about the Covid situation - totally acceptable, no problem. He continues to go to work every day despite the worries about germs etc. He saw DCs once in April, and then not again until July when lockdown was lifted a little and he took them on holiday.
So as not to drip feed, eldest DC was 15 at this point and had refused all contact with her DF for a good while (since January) due to him constantly letting her down and lying to her.
ExH took youngest 2 DCs on holiday for a week, me and DP took eldest DC on holiday for a week, no problem.
Since this time, the two youngest DCs have visited their DF every fortnight from Fri-Sun as per the usual arrnagements.
Fast forward to this lockdown and when the announcement came in about the new strain of the virus and the schools closing, I text exH to ask for his thoughts seeing as exMIL has underlying health and trying to be understanding that she may be anxious again (and quite justified too). Response from exH is that MIL doesn't want the children there to stay, worried about germs, and could he arrange to come and take the DC out for walks instead? I agreed, but also reassured exH that DC have not left the house since they visited him at xmas so have had no contact with anyone. Also highlighted concern with him being fined for being out of his usual area and walking etc, as per the reports on TV about over zealous police issuing fines. That was 7th Jan and I heard nothing back from him at all, until yesterday when I got the most garbled text I've ever had, asking me what the plans were and if I would be prepared to take the DC to him if I wasn't prepared to allow them to travel in his vehicle 
I genuinely was really confused by this so phoned him and exMIL answered as he was in the bath.
She immediately started asking me why I was stopping the DC from having contact with their DF, why I wouldn't share the transporting of the DC between us and how dare I treat him like that after all he has done for us during lockdown.... well by now I am totally and couldn't help but burst out laughing - which just pissed her off.
The upshot of this is that she has no underlying health conditions, despite her and exH making a really big thing in the past of her hospital admissions for respiratory issues and asthma. She stated she is not anxious and told me I am just using it as an excuse to not send the DC for time with their dad.
Apparently all 3 DC have told her in the last few months that I don't like them going there (except she has spoken to eldest DC for almost 2 years) and will do anything to stop them. All 3 DC refute this entirely.
She also asked why I won't share the transport with exH and sometimes drop the kids off or pick them up. Told her straight that until lockdown 1 we were doing this every other week as agreed - but that is all forgotten about. Apparently, I am only happy to transport the children to exH when I want to get rid of them 
I'm afraid it was at this point I got totally pissed off with her, called her a poisonous old bat and told her to fuck off before hanging up.
Lost the moral highground by yelling at her to fuck off, but boy did it make me feel better.
ExH will continue to hide behind her apron as he cannot cut the strings and she will continue to be a loopy old witch, but hey ho, DC 1 made her own mind up as everyone said she would and the 2 others will follow suit before too long.
Rant over.