Thanks Jim,
I added about 3 cm of thick fine-stranded copper wire to my 700 ml of solution and left it overnight with the air pump going. The next morning all the copper had dissolved but the solution was quite dark, indicating that the copper (1) had not been oxidized to copper (2). I added 10 ml of concentrated (pool chemical) HCl and there was some improvement after another night. I added another 10 ml of HCl and now it looks terrific. I tested a tiny sample with a few drops of 6% H2O2 and there was no change, which I think means that oxidation using bubbled air was complete. I'm going to try etching a small piece of board to see whether it? can stay oxidized but I won't have time to do that for another couple of days due to other commitments. It does seem that the fix was to make sure there was enough HCl present. I don't have a pH meter but I imagine that one would be quite useful.
Watch this space!
Morris
