Update....
Even though Dolan maintain they have never seen this issue before, the frame design has since been changed and the new frames have the cables routed directly down through the head tube. I'll let you all decide whether that is a good thing or not but at least it will mean this can't happen again. I now need to box and send back to Dolan at my own cost (£50 apparently) and when the new frames come in they will rebuild my components onto a new one and send it off. I've been given a date of mid Feb for this but seeing as the original delivery date when bought was 2 months out, I'm not too confident of this being correct, but we'll see.
I hope this experience helps anyone who may be contemplating this bike or the rim brake version as per the original thread.