Thanks for your help and advice, Steve.
I got a pair of Belgian coticules following LX Emergency's advice. They should arrive here soon - currently on their way to me from Germany. Once they get here, I will try honing on the rougher one (yellow/white if I remember correctly).
I'm sure I've dulled it on the CrO side of the strop, but if I can't sort it out on the hone, it's going back to LX.
I think you are right about stropping technique too. I don't think I have kept a light edge when stropping. I need to pay more attention to this and also to keeping the blade flat.
I should point out my razor is a Stainless one. Does this explain why it's so difficult to sort out?