Sorry, I should have responded before now no how this turned out.
I phoned them and talked to an adviser, something I would not normally do. I then got a supervisor to agree that the action was unnecessary as I was paying (they did not get confirmation from the back before serving the papers) and that did not actually take the papers into court. I have a letter saying they will not take the papers into court as long as the payments continue.
It ends well for once.
Thanks for the advise.