As a Ukrainian living in London I'd say that nobody in sane mind in UK, and probably in EU will let Ukraine join EU. Mind Greece and Cyprus.
Check the numbers: http://atlas.media.mit.edu/country/ukr/ 25% of export and 36% of import are Russian goods, several times more than EU combined. Sign that agreement as EU pushes it - Ukraine would be isolated, poor and really unhappy.
Whatever is my opinion is not important, but "huge majority" of 42% shouldn't be allowed to force their decision to "only" 31% minority. I think Janukovič got it right here, not wanting to side with any side and trying to just keep it as neutral as possible. It is not a good idea to decide about such a big topic like future of the whole country and which union to join based on such a small "majority".
In the long run, the best thing is to just do nothing right now, and try to reach some kind of compromise in a deeply divided country that is equally acceptable to both sides. Whatever that compromise might be, going west, or going east, or peacefully splitting the country in two/three parts, everything is better than inevitable escalation that this leads to.
[http://eeas.europa.eu/ukraine/assoagreement/assoagreement-20...]