OK so my S20 had been sitting in the bottom of a drw for over 2 years now after emitting the E28 error and canon quoting me for £130 to fix it (although they did offer a 6 month warrenty, I now discover that they just send all there canon digital work to http://www.lehmannsdirect.co.uk/mainindex.asp
although I have never approached them to quote).
Anyway, after reading all these posts, I charged up the battery and got the lens out, gave it a few random gentle raps with my fingers and then, lo and behold, roberts your mothers brother, the thing started working again!!! Hurrahh.. how long for I dont know, but if it fails I will post again.. and might consider opening it up and looking at these here dodgy connections. Then, if all else fails, I'll pay whats required. It was a great camera when it worked, and its still cheaper to get it reparied than getting the equivalent second hander of ebay.
Thanks to all that posted!! You have trully made my year!!
Nick