Jason Plato definitely has a not-nice side. I received a rude and unnecessary email from him once after criticising something he'd done in a BTCC race on a blog I used to have. I assume it actually was him.
How long ago did you meet Jenson? He used to be really down to earth and pleasant, it's since his world title that he's disappeared up his own bum a bit.
Year before last, so after the world title and he'd joined McLaren. It was via a sponsor event though, so maybe he was on best behaviour, but I found him to be charming, funny and really approachable.
There was quite a funny incident with Plato a couple of years back. Some bloke described meeting him on a forum and talked about how Jason was weird and standoffish. Jason joined the forum and posted a very full and frank rebuttal which basically described his impression of the guy.
The fan said he was really nervous and couldn't believe his luck. Plato's side of the story said the guy came across as a total weirdo who wouldn't let go of his hand after shaking it, and followed him into a shop when he was collecting his dry cleaning!
It's a perfect example of how there's 2 sides to every story, and neither of them could see themselves in the wrong.