Hi Maffew, I read the first dozen pages and would make the following observations:
There are a number of small grammatical errors, the second line of action for example, a can drops to the floor and roll to the kerb. Other similar instances as well.
At one point, Amy seems to be called Jess, and Ellie and Ellen seem to be interchaingable which just makes it harder for the reader to keep up with.
There is no need to indicate the end of a scene, just clearly show the start of a new one.
A transition is a means of getting from one scene/shot to another. If you feel you need to dictate this then you should indicate CUT/FADE/DISSOLVE etc otherwise, just start a new scene. If you move from the bar to the toilets it is a different location and therefore a new scene heading is required. This is where I gave up as it was chopping from pub to toilets to dance floor to wine bar to flat without much indication of scene changes.
As mentioned previously by other posters, there is too much exposition. In the pub, Ellie has a big chunk of dialogue recapping Dans situation and we already know it so I would say it's not necessary to tell us again.
The action should be more consise. In the pub you say Ellie does the universal finger symbol for having sex, then go on to describe it. You don't need both. Similarly, you describe Dans gesture for gay sex and then tell us what it is supposed to mean. Incidentally, I thought his bumping his fingers together was very funny.
I was unsure why Ellie would be lugging round a polaroid camera when it seems everyone these days has a mobile phone with a camera. It just didn't seem realistic. If she has a particular reason for making that choice I think we need to be aware of it. Maybe she's paranoid about getting a tumour?
As already mentioned, it didn't feel like a sitcom. Sitcom characters are trapped in their immediate situation/circumstance and this is, generally, emphasised by limited locations. There are also bugetary considerations that any producer would take into account.
Having said all this, there were some interesting images and it had an OK feel about it. I liked a lot of your scene where he wakes up in the playground although not sure how easy it would be in practice with swearing at children.
I think if you cut out the transitions/scene ends and duplicated action you'd find it was falling quite a way off the 6000 word mark so you will need to address the length issue too.
Sorry if this all sounds negative and good luck with your next draft.
it's the negative stuff I was after - going through some pretty radical changes now. Changed the beginning with dan waking up in the school, Amy is now a teacher.. as such the conversation in the pub changed - ellie is a full blown gay now - got rid of all the exposition and re-wrote a lot of the dialogue. 
