Drivers are meant to have their vehicles under control at all times, regardless of the jurisdiction or rules. While cars cannot stop on a dime, I think the UK is a very pedestrian unfriendly country when it comes to crossings.
If I am crossing a side street, I should not have to yield the right of way to turning traffic (or traffic entering from that side street or driveway for that matter) if I am crossing with a light. I would not have to do so as a car in a lane that turning car would have to cross to complete the turn, so why should I as a pedestrian? Why should I have to yield the right of way to vehicles pulling out from driveways? I don't know if it's the law, but I know it's expected of me. So much so that one time I was walking down the pavement in front of the Streatham bus depot, and the driver of a bus (who didn't stop at the line before the pavement) had the cheek to honk his horn at me as I crossed the access road. Again, if I were a vehicle travelling legally in my lane of traffic, he would, as a vehicle entering traffic, would have to yield and wait for me.
Pavements should be a place where pedestrians always have the right of way without question. IMO, so should crossings where pedestrians are using them legally. In the case of zebra crossings that means anyone who has their foot in the crossing. It's a driver's responsibility to be alert, and if he or she is missing something like people entering a zebra crossing, how is he or she meant to see defensive driving situations where someone might be in the wrong and step out in front of a car (or turn into a driver's lane) but an accident can be avoided by quick thinking?
As for me, I practice defensive walking. I wait at zebra crossings because I've seen idiots breeze through them like they aren't even there. If someone decides to ignore one either consciously or out of ineptitude, it doesn't really matter if I am in the right or not. I could be injured seriously or perhaps killed.
Road courtesy really has to include the realisation that pedestrians do not have anything protecting them from massive metal boxes driven by people who can sometimes be in too much of a hurry to get to where ever they're going. IMO, all jurisdictions should have laws that protect pedestrians, encourage foot traffic, and encourage driver mindfulness. Really, you're going to get there before me in your car, kindly don't kill me in the process.