Yes you do another position statement. A position statement "updates the position" so it's anything that has happened since the last one, plus anything else you want to say. It specifically seems to be asking for proposals for child arrangements ongoing.
So I would write a new one. You can include anything you want from the previous one but I wouldn't copy and paste directly. You can also update that the Mother failed to attend the enforcement hearing.
My concern about this situation is it's being dragged out. The Magistrates may have been nice but delay is harmful to the child. A section 7 will take ages!
I think I'd be looking at submitting a C2 for an urgent directions hearing with a District Judge saying the Mother must attend the hearing. And request that, at the C2 she is required to follow the existing order.
If she doesn't turn up at that one, then you could ask for transfer of residency maybe. There was a case a while back where a Mother failed to attend 3 hearings and actually refused, and the Judge transferred residency.
My concern is the timescale. You haven't seen the kids for 6 months. It could be another 6 months by the time a section 7 is done and another hearing and by then no one will remember what those Magistrates said. Cafcass could well say the children are happy and doing well in the Mother's care and recommend gradual progression again (which the ex will probably disrupt).
You don't want this dragging on for years and the children becoming alienated.
I will have a think about this but I wouldn't just accept going away and waiting for a Section 7 report when the Mother didn't attend an enforcement hearing.
Another option, if submitting a C2 is to submit a part 25 application for an Independent Social Worker. This costs money of course. Could be about £2,000. They can do the Section 7 much quicker and are experts in saying if there is alienation (which frankly, Cafcass are not). It could all be done within a couple of months and maybe even a recommendation to transfer residency if the Mother doesn't comply with orders.
I think it needs dealing with robustly. As the alienating parent, she is happily getting on with her life for up to a year or more, while you are waiting and losing.