RTI, EYU, P-60 problem

[chris777]

I've been using rti basic PAYE tools since Jan of this year. (I'm a new start-up)
I'm the only employee.
Due to a family crisis I was late trying to submit the FPS for my month of March pay. I tried on April 21st but 19th was the cut off date.
Basically the FPS submission failed. I rang technical helpdesk and they said delete the payment entry under my employee record as it was too late to submit it after tax year end.
Instead create a EYU for the amount, £858 gross.
I did that and that submission was accepted. OK so far.
Problem arose when I tried to print a P-60 for myself today and the total pay figure does not include the £858.
Also I noticed that my HMRC PAYE account online was showing I owed £200 (£100 tax, rest NI = £54 Eer, £46 Ee NI )(there should be no tax or NI payable)
I phoned the HMRC employer helpline - they were unhelpful to say the least and left it all in my court.
I checked the original EYU submission and I did include my tax code.
I don't know how to solve this technically and am worried about the £200 the HMRC say I need to pay as I don't have the money.
If you've read this far and can offer practical advice, thank you.