Yeah, nobody checks. A flatmate of mine had her boyfriend stay for a week and nothing happened. I'm not sure about Pollock, but in self-catered flats you don't even have to register the guest as staying in your room.
I should mention that that's based solely on Robertson's Close experience. Also, people can sleep on the couches in the kitchen. I forgot to mention this in my original rant about Robertson's, but, the couches are unbelievably horrible. You get two (at least flats 8 and 7 did, refer to my previous post in this thread if you desperately want to know how many couches you'll have), and they each seat 2 comfortably, 3 if necessary. If you push them both together they make a reasonably comfortable seat for one person, but you have to be either locked out of your own flat or drunk to sleep on one of them. Not just "teehee, I nearly used the wrong key to get in" drunk, full on "wait... what year is it?" drunk. If you go for the kitchen, prepare to be brought out of your light slumber by a flatmate coming into the kitchen in a morning-zombie state, turning on the light, saying "oh, sorry", then exiting. Consider that the smallest flats at Robertson's hold four people, each person will do the same thing. In short, unless it can't be avoided, go home instead of sleeping on someone else in Robertson's couch.
Diagram time! Seeing as I just spoke about kitchens, I'm assuming everyone's at least a little curious about what they're laid out like. Here's what flats 2, 5, 8, and 11 in block 9 are like:
http://img441.imageshack.us/img441/8002/fl89rckitch.jpg . Sorry for how terrible a sketch it is, to be honest I lost interest halfway through.
Anyway, enough about kitchens. I noticed that somebody posted about putting up posters in the flat. Guidelines insist that you use thumb tacks. If you use blu-tack, the worst that will happen is you'll get a note on your flat inspection summary sheet that says "please use thumb tacks instead of blu-tack for your posters". Unless you damage the walls in a serious way, I doubt anything will happen.
A quick note about smoking. I can't incriminate myself, because my username is very close to my actual name, so let's say this is for conversation's sake. Hypothetically, if all of your flatmates smoke, designate the kitchen as a smoking room. Leave the window open when anyone's smoking, if you do so the fire alarm won't pick up cigarette or shisha smoke. Similar types of smoke are fine too, if you catch my drift. However, I've never seen anyone smoke a cigar at Robertson's, so don't be the first to discover that their richer smoke sets of the alarms. Of course I wouldn't recommend smoking in your flat, and have never done so myself. But, for the sake of conversation, if you were to blitz the place with air freshener and Febreeze before a flat inspection, I'd expect that the inspector wouldn't note the smell of smoke on the official record. Purely as a hypothetical, let's say you were away for a week during which a flat inspection took place, and you'd left an ashtray full of butts on the desk in your room. All that would happen would be a note on the inspection report under your room's section that said "NO SMOKING IN THE FLATS!!". It would most likely never be followed up, and no fine would be incurred.
Well, I'm quite tired now, so if you're interested in unnecessary detail about Robertson's Close expect more tomorrow.