Replying to this and xfpd.
Wires are colour coded and 5v and GND are red and black so wired correctly, green wire goes to the analouge input although it is blue in the wiki. Can try and transpose them to see if it makes a diference.
As per the instructions on the wiki, the switch was set to 'D' although connected to the analog inputs. Setting it to 'A' is just a stream of values between 300 and 800 and again, touching the piezo film or even removing it made no difference to the output. I sholud note that I bought 3 of these and all react the same. Also have 2 Arduinos and tried with both.
The project is at where I work so will add the output tomorrow whan I am back but with the sensitivity pot all the way up it is just a stream of 1023 and all the way down it is fluctuating between 16 and 17. inbetween it randomly shows either. touching or removing the piezo film makes no difference.
The broader picture is to find a sensor that I can attach to something, piece of wood or some structure and will detect someone knocking or tapping it and then act upon that.
I have tried piezo elements but cannot get them to work reliably. I thought this may be a better option but open to suggestions.