Please help - Nightmare with Restons Solicitors & Arrow Global

[Caddy]

A few months ago I was contacted by Restons Solicitors saying that they were acting on behalf of Arrow Global (who had bought my Marks & Spencer debt from 2003). I filled out a financial statement, as they requested and I agreed to make payments each month. The following month they issued a CCj against me for the whole amount. I agreed that I owed the money and that I was willing to make payments each month so I was told to send an income and expenditure form to the court. I contacted the court and they said to make contact with Restons to make the payments, which I did and it was agreed. 4 months later (now) I have been contacted with another letter, saying that if I don't pay in full (£8,000), they will take me back to court. I am very worried and I have jumped through hoops with this company. Should I make a CCA request and can I have the CCJ overturned? Any advice would be greatly appreciated.