Andy, My bike has been doing the same thing for a couple of weeks now. I turn the ignition on, hit the starter button, the clock resets to 00:00 and then it starts. It has also increasingly struggled to start over the past few days, and now it won't start at all - hence the reason I am sat here at home instead of in the office at work.... When I press the starter button, there is a click, all the displays switch off, there is a faint light behing the neutral light and the rev counter goes a little crazy, flicking round to 5 or 6k rpm. My bike is three years old, 1150GS, 23000 miles. I am hoping its the battery and that a new one will sort things out, but unfortunately I can't offer you any further info as my electronics knowledge extends to wiring a plug.
If it is the battery, presumably I can phone halfords and see if they have one that matches the tech spec from the handbook (i.e gel, 12v 19Ah, maintenance free?