Well, I got to the tube station and it drew a blank. Nothing happened. I took the back off my phone and tried it face down against the reader, but no joy. I removed it from the phone and tried it "naked". Still nothing. And then I noticed that the aerial had come away from one side of the chip! Damn and blast it's fragility!
So, I'll pick up another one (I've got lots of nail varnish remover left) and give it another go.
I found this video, so I know it can be done. It looks like I may have to run the aerial all the way round the case back to get it to work properly, though.
Results to follow...