Why you should always assume the driver has not seen you

a) i agree, but don't think it would have made much difference
b) & c) i like to hope i'd do as you suggest but i don't think i'd have noticed the Mondeo soon enough to either. I don't think this was a matter of seeing the risk and choosing to chance it, i think the risk zoomed out of the background too fast to be avoided. Also, read what he said about having both brakes ready below:

I take the centre of the lane when going straight, this makes my intentions clear and prevents impatient people from trying to force their way past or overtake in stupid places. This also means I have both brakes and the bike under full control.
This guy came fast and was outside what was then my danger perimeter when I entered the roundabout. The roundabout was clear when I entered. When he arrived, he failed to slow and accelerated across the line I was suddenly in his kill zone. I couldn't accelerate to the speeds necessary to get out from in front of him before he hit me. Nor could I suddenly go into reverse. A left or right turn just puts me closer or further from him and stopping means I give up and wait for the 2 broken legs.
Indicating was not an issue here despite what my new friend above repeats. The driver simply didn't see a cyclist and accelerated ahead of the black Audi.
Apparently my friend above thinks I should have been riding one handed, wobbly indicating a U-turn, then all would have been well!!
I could have been stationary at the point he crossed the give way line. I would still have been hit from the side and likely sustained 2 broken legs.
It's obvious that we have to look out for stuff. But sometimes there are circumstances where you suddenly have no escape route. When a car blindly accelerates out of a side street as you are passing, unless you can do an amazing bunny hop, your options are pretty limited. I guess there is a balance to be struck. You could walk down the street assuming every other person is about to stab or shoot you, but that makes for a pretty scared existence and is an overreaction to the actual level of threat.
The guy made a mistake, the human brain works that way, it sees only what it looks for, the rest is filtered out as background noise.
I was simply in front of him when he drove through the piece of space that I was passing through. He was faster than me and much wider. There was no way to get out of that danger area in front of the moving vehicle before he reached my position.
I don't feel any need to attribute malice or stupidity, he just screwed up. And some car drivers don't like to face up to their responsibilities when handling what is in fact a very powerful weapon in a public place.