Success !!
Am now offically done with DC. My last redemption was in March, but I was still waiting for the cash portion of a GRU-EWR-BER cancellation to come through. I had cancelled back in Dec and the miles came back within 24hrs but no sign of the cash. I finally called them about 10 days ago. (called customer services # in the UK as found on the contact us from BA Ireland homepage). Agent was helpful and said she would raise a ticket with refunds.
A week later called again as no sign of any action. Another 15min call - mostly waiting on hold while agent investigated. Finally she came back and told me she had escalated with refunds. 3 days later money from BA appeared in my account (when submitting the form, I gave details of my Irish bank a/c as I did not want the hassle of a £ cheque arriving in the post).

All in all am quite relieved. I was preparing to go down the small claims route but no longer need to worry about that.

Farewell DC, its been great