[update]
Hi guys
Eventually bought a Logitech C270 from Amazon for £17. Works great, I've had it running in guvcview, taken stills and recorded video with sound. Also works very well with Skype which is the main reason for the upgrade, the video quality is 1000% better than the built in camera so I'm well pleased. All just worked straight off, very impressive.
[edit]
I unplugged the webcam to try it on my wife's laptop which does not have a camera, the video worked fine but I couldn't get the audio to work in skype no matter what settings I tried. Plugged it back in mine and same thing, audio wouldn't work at all in Skype, did before but not now! Tried everything with no joy until I tried turning off Pulse Audio... Worked perfectly! just had a 30 min call with my daughter, no problems whatsoever, video and audio perfect. I have no idea what that's all about but glad it appears to be fixed. I'll try it again on the other laptop with pulse audio turned off and see how that goes, that is also running M4. [I'll be back]
[2nd edit]
Turned off Pulse audio on the other laptop and again the sound issues disappeared! Works perfectly in Skype (tested on a live call) go figure. Still happy though
Cheers.