>> If you are brave, you can try taking it apart and putting it back together again. But only if you take full responsibility for what happens. :-)
Actually, your mention of 'crosswires' caused me to look under the keyboard. I can see 8 thin wire connectors that are obviously sending the input from the keyboard.
One of these looks bent and is not hooked in properly. Therefore, I bet this is the cause of the problem, as the problems occur on certain keypresses (such as space or Fn).
As I am unable to poke this back in place, I'm going to have to take the bottom cover off (once I can buy a tiny screwdriver) and attempt to re-insert the connector.
I don't really see that I have much to lose.