Re: Window tinting, depends also on plod's attitude around where you stay.
Personally, I would want all rear and front side windows done. I think B pillar back looks wrong and half finished.
A subtle tint shouldn't attract too much unwanted attention from the Police but too dark and they can make you remove them at the roadside.
Last car I got tinted was back in 1998 and that was with Pentagon in Glasgow when I opted for the 2nd darkest; Midnight.
Back then there wasn't really a law as such and you could more or less do what you wanted - except tint your windscreen of course.
These days I think even the light smoke tint (in front of B pillar) is straying into the wrong side of the law but it seems almost pointless fitting anything lighter than Smoke.
http://www.pentagonglasgow.co.uk/tint-shades/