Thank you that was what I needed - and yes hindsight is an awesome thing
You are free to use your name for the children at holiday clubs etc - but not anywhere "official".
To use a double barrelled name - or even use it as a new middle name - you need either the consent of the father or an Order from the Court.
The Court is very reluctant to agree to a change of name in general circumstances.
However since you wish to double barrel rather than change you have a reasonable chance of success.
However do not stress that you so not wish them to feel "different" - it is not an unusual position and many of their class mates will be in the same situation.
Also when dealing with anyone else do not talk about "allowing" contact - it will give the wrong picture of the flexible approach you actually use!
The starting point is to try and discuss matters with your ex using Family mediation - you have to attend the Mediation Information and Assessment meeting even if he will not.
If that fails you can apply to the court for a specific issue order using a form C100 and paying the fee of £215.
Take a calm and measured approach and emphasise that it is a way of linking the "new"family without losing the old.
I hope that this is of assistance please ask if you need further details