No Peter, I never said that I had defaulted on a repayment plan with the bailiff, I defaulted on the agreement I had with the court. Only heard from the bailiffs for the first time last Thursday.
Particular thanks to DX for their advice as I contacted the court and they have admitted they failed to follow process. It seems the Final Steps Notice was not sent. I have had an email from the bailiffs today stating the whole £310 has been written off because the debt was settled with the court. Very relieved although it seems fair given their failings.