It is important to agree a Consent Order and then get the courts to seal the order. Once sealed, and if it is a Clean Break, then the court will take a dim view of requests to vary the order. They will allow a consensual alteration but these things are supposed to be final and binding - they don't want people continually tying up the courts over squibbly little alterations.
For me, the mediators never encouraged us to write up a Consent Order. They left it as written summaries. I thought this would suffice but I was wrong about that. Since my ex has moved out of the country, the UK court does not have any way to enforce an order anyway. We can't go back to mediation as does not live here and does not come here to visit the children or for work. So I encourage anyone in this type of position to get more security around their consent order. I could have been more aware about what to do, and I certainly regret that.