Quote from NielsenDK:
I am often in London and the people i talk to are divided on the issue. The media is pretty much against it, and the people pick that up. But most people don't want to dig into what the EU is all about and what the Euro can or cannot do for them. And the EU is certainly not helping in providing much public info about what it is. So they would vote no. They do like the pound, it is part of their history. It is what they know and trust.
This is what happened in Ireland as well. They voted no on the Lisbon treaty, not because they didn't like it, but because they didn't know what it was about and they were happy with what they had.
Some people are a bit reluctant to the EU, because they do not know what's in it for them. And then their national pride helps to make the decision for them. They stick with what they have and trust.