Parents rights to take children

[Otterbee]

We have a divorced couple... divorced for 3 months but separated for 2 years.
Two kids have lived with the Mother since the father left but opted to move 15 miles away from Father, so changed schools etc.
Kids were seeing father over weekends and holidays.
Mother is needing to move house (unexpectedly) which has left her and kids needing to relocate.
Mother agreed that kids should go back to live with Father for a couple of months while she finds a new house back near to the Fathers home, which has meant they have changed schools again back to their original school.
The agreement between Mother and Father was that this was ONLY going to be a temporary solution having the kids live with him, and during that time Mother has agreed not to receive any CMS payments.
Mother is now being told by Father that he is going to attempt to take the kids on full time, so has allowed the Mother to go far enough down this planned route (to the point where the kids live with father for 1 week and have just started school) where it is impossible to reverse the situation.

So, the question here is... what rights does the Father have to dictate whether he is going to "take" the kids, which is clearly going against what was previously agreed?

Who can the Mother talk to who has any authority in these situations that could tell the Father that he cannot alone make these decisions without the Mothers consent?

The mother needs legal advice.

Sounds like 50/50 makes sense here. Both parents want and are able to fully care for the children.

If they can’t agree a fair split together, they both need to get a solicitor. If it gets to it, the court will decide a fair split. Father can’t just take them full time without mother’s agreement, should be the same visa versa but rarely the case that way round. I think the mother needs to engage a solicitor to get the ball rolling as the current person wanting to change the ‘status quo’.

She needs legal advice, if both have parental responsibility but she has nowhere to live he's in a strong position. Once she does have suitable accommodation 50/50 custody is likely unless there are other factors involved eg abuse, substance misuse and so on

I think she needs to visit a solicitor

"Who can the Mother talk to who has any authority in these situations that could tell the Father that he cannot alone make these decisions without the Mothers consent?"

There isn't anyone.

Why do you think the father is somehow the secondary parent?

Is the father concerned about the moving about? What are his reasons for wanting to be the main parent? I'd be pretty annoyed if my kids were moved schools and moved back again in a short period - incredibly unsettling for them.

I would suggest 50:50 care.

I think the mother needs legal advice. What do the children want?

what rights does the Father have to dictate whether he is going to "take" the kids, which is clearly going against what was previously agreed?

If these people are in England or Wales, the parents do not have any rights over their children. The children have rights, parents have responsibilities.

I agree with pp, the mother needs legal advice.