Thanks Ray. To be fair, the link in Chris Partington's post has lots of useful information regarding piezo transducers. I was particularly interested to learn that several pick ups connected in parallel require a lower input impedance than just one. There is also a link to a '1$ pick up' page.   

If you have the right tools, the right skills and the right information you can make all the components in the Pick up - Carpenter jack - Impedance matching/pre amp chain for less than £20. Without the skills, tools or information you'll be best off buying guaranteed stuff.