Just want to add something here.
Biggest peice of advice i have taken and really glad i took it was to "take primary" road position as much as i can during my rides.
It really does pay to hold up traffic and piss of drivers rather than them pushing you, ie the cyclist into the drainage part of the road.
Kidding aside though, if you do take primary it is safer, but you WILL get abused to hell from drivers, something which i think needs to be addressed maybe through the DVLA and their exams.
Example of why,
Going down a road with a school nearby thus lots of badly parked cars along the road, both sides.
As i coming up the road traffic coming towards me, with a parked car ahead, i have plenty of time to get ahead of parked car before car ahead comes near....
As i do my "safty check" over shoulder before going around the parked car another car wizzing from behind me overtakes, but fails to do so properly ,thus has to pull in front of me and cutt me up thus blocking me into the parked car.
This is what pisses me off a lot, taking primary position and still people try to push you off the road into the drains..