On my way out tonight and I felt the throttle cable go.
As there is nothing when I open up the throttle it seems obvious which of the two cables has gone but as it looks as though most of the plastic has to come off I'm going to replace both.
At the same time I'll check the valve clearances.
Based on other posts it'll take 5 hrs for the cables and maybe another hour for the valves if all goes smoothly.
Wish me luck!