OK thanks all, still not working, but some observations. I've checked the strips and cleaned up a bit (messy soldering, how dare you!!!
) I've run a craft knife down the gaps to clean up, and all looks fine. Still no joy though. However, when I turn the pot, I get a small amount of static crackle (fairly faint) and also when I touch anything on what is nominally the input side of the board, I get a sort of very faint mousey squeek. Not the tracks, just the components. Yes I am using a dual opamp, specifically an LF353N, but also tried LF412 which was the same.
What I don't get is that the pot on this diagram appears to be connected to earth on both sides (lugs 1 and 3). Can that be right?
I should get the rest of the proper parts for this in a few days, but I would have thought C500K pot would have worked in place of a B500K?
I've seen a PCB layout for this device which appears to put the input source on the other side of the opamp, could this be the issue? I.e, the wrong input for the opamp being used?
I have literally NO idea what I am doing.