child arrangements order/ PSO question ( cross-petition?)

[firestarter2]

I am dealing with a difficult situation and seeking procedural advice regarding a Child Arrangement Order and PSO filed by my ex-wife just over a week ago.

Background:

1. Mediation Bypass: Ex refused to engage in mediation. I suspect ex may have claimed abuse (possibly financial) to bypass the requirement for a MIAM (After our split, in an argument ex said all monies sent to me as contribution to the bills etc(my house outright), even her phone payments that was in my name lol was actually owed to her and I should pay it all back & I ignored just assuming it was out of anger). I was never abusive in any other ways and ex has never accused me of such til now.
2. Lack of Contact(3yr DS): ex went AWOL after a year into our divorce and started to ignore all requests for visitations which had been one weekend every month & 5 days during my work annual leave every quarter as they are 300miles away. ex only ever communicated about the property and financial matters so I know ex ignored other messages.
3. Current Status: Her solicitors informed me last week of court filing and I am yet to officially be served.
4. Her grounds/relationship with DS: Our relationship was perfect til the last month, I was hands-on parent and partner since day 1, ex was SAHM, ex lived rent free since day one and only ever contributed when ex got an inheritance in the last 2 years and I was off work for a period due to illness. Ex moved 300miles away to give her room to fix living arrangement and eventually this became permanent as cannot afford expensive rents near me so I agreed & I continued to drive once a month to spend a weekend with them. son was moved 300 miles away from his previous home (and my older children/his half-siblings) by his mother.

My priority is establishing contact, if just 2 days a month and I can finance the travel myself. My son has older siblings(my older kids who I have 50/50 custody) and they had a good relationship with him and they miss him dearly. I trust my son misses me also as I was with him every single day of his life since birth until separation.

My Question:
Given that her application has been filed but not yet served on me, should I:
A) File my own court documents (C100) now with my desired contact proposals? B) Wait to be formally served with her application and then file my response (C7) and cross-application/proposals?. Do i have to have a solicitor or can i just handle this on my own

Any guidance on the standard legal procedure in this scenario, or on how to best frame/defend myself in these proceedings would be appreciated (I was also going to do a PSO as I do not trust her any longer and her intentions). Our personal issues shouldn't have driven her to influence the child arrangements but we are here.

I think you need urgent legal advice. Now. Stopping contact I think would usually mean you would put in a C100. However this situation is more complicated.
The roles were reversed in my situation, contact was stopped by me for safety reasons. It took about 10 weeks from ex putting in application to first court date and a temporary contact plan was put in place from them until the next court date.