Thanks for the offer mark. I'll be in touch shortly
I got the cheap Maplin supply hooked up and once I realised that the connections are inverted (two battery terminals have to be inverted to work together) I tried it.. There's a hum through the speakers from the supply which I think is lack of smoothing (I'll have to make my kit of parts up pronto).
As an aside, the Lentek works on 3V, the test light only just beginning to dim out compared to 6V+
Tear down these walls; Cut the ties that held me
Crying out at the top of my voice; Tell me now if you can hear me