Regarding accommodation:
Lakeside and Heronbank are stil more or less on campus. It's maybe a 5 minute walk to the Eastern lecture halls (~400m) with possibly 8 to the library (~600m), depending on where exactly you live and how fast you walk.
I haven't been in any of the rooms myself but I've heard good things about it and either Lakeside or Heronbank would certainly be my favourite choice - if I could apply to them. Unfortunately, I can't (for very stupid regulatory reasoning which I fail to fully understand - apparently, you're not allowed to apply for on-campus accommodation if you have been a postgraduate student before any point in you life, regardless of whether you lived on campus before - while living 1st/3rd undergrad and 1st postgrad year on campus is possible).
The other major postgrad hall is Claycroft. In fact, these are three big buildings and they are located on the other side of the campus, in the very West part. Main advantage: 4 minute walk to a huge Tesco (300m; 1,400m or so from Lakeside/Heronbank [<20 minutes]). Main disadvantage form my point of view: Having to share a bathroom with one other student (of your gender). Rooms are spacious for halls terms in the UK.
Maybe because I've studied in London before, but I really don't think that distance should be any problem if you live on campus. Unfortunately, many of us will not, hence you might want to think about a bike or car if you're living in Leamington, (central) Coventry or wherever.
Last but not least: Not many postgrads I have been in touch with spent much time at the Student's Union in the Southern part of the campus. Frankly, there's nothing there to spend time with except for a few restaurants, a pub (well, this was regularly frequented, admittedly) and for the occasional party/club event. Apparently, a new postgrad-only space has been recently created not too far from the library which is located quite centrally. But, when it comes to procrastination, I suppose that at least some of you will be either at the library (and not study), the Arts Centre (between library and Student's Union) or, if procrastination isn't your thing, at the Learning Grid in the Northern part of the campus. The only alternative: The Sports Centre in the somewhat Western part.
Conclusion: If you want to go to Tesco (or Boots, Iceland, and a few more) daily, or want to work out daily, you might want to opt for Claycroft as it's just more conveniently located and a little cheaper. Lakeside/Heronbank are a tad more expensive but you have your own bathroom and probably also a quieter room, although this obviously also depends on your neighbours.
I can't say anything about Tocil and the other (?) option. Nevertheless, just keep in mind that places are limited and not all of us will get a place on campus anyway.
Edit: PS: As many of us are social science students - the main social sciences building is located in the 'mid-Eastern' part of the campus, east of the library. From Tesco, I usually needed about 15 min to get there (should be 10 from Claycroft and probably around 6 or so from Heronbank).