I do finding the polling on this very bizarre and it may be that there are too many moving parts in this whole referendum to try and get a proper fix on things due to the undecided and turnout issue.
Most forums I've looked on have leave ahead - this may be an interesting site for you as it has leave on 87% and I understand that it is based on circa 25,000 votes so far but I can't verify that as I can't access some of the data or vote due to my non UK IP address - whether this has been subjected to multiple voting by an army of spotty UKIP techies is the question
http://www.pollstation.uk/eu-referendum/poll/