some great ideas here, thanks for all the responses.  Being an engineer means I don't think i can resist the temptation to go the DIY route with a bunch of piezo's, and see if i can get a decent sound for a fiver   Have also just found my dads old piezo he used for his acoustic guitar, so that'll be my starting point.  If that all fails, I guess my wallet will take the hit. 
 
Edit: Seems it might not be a piezo pickup, it's a FRAP (flat response audio pickup), so might be terrible, but it has a box with batteries and a jack socket, so that could prove useful.