The undemocratic nature of the EU is really the core of the issue for me, I doubt it'll budge on that and the reforms DC got were more menial instead of the fundamental reform I think the EU requires. When you look at what happened in Greece it doesn't shine a lot of optimism for the EU, and it's economic policy enforces austerity across Europe and makes it impossible to follow the left side of the labour party, which whether you agree with or not if Europe denied them their economic policy after they were elected it would be a disaster for democracy.
In terms of immigration I think EU migration in general has been good for the UK economy, I think Blair and Labour made a mistake with allowing A8 migrants to come and work so quickly (which the rest of Europe didn't do) but migrants help fill jobs and help to balance out the ageing population.
People get worried a lot about the border issues. If the UK leaves it won't stop people coming into the country. Switzerland isn't in the EU but people can go there without any trouble.
That's because Switzerland wanted to be in the trade bloc of Europe without having to enter the EU itself, so joined the Schengen area to allow free movement of labour, the UK did not want to be in the Schenghen area so we have some strings attached (we can check peoples passports)
To be honest I'm pretty torn on the issue, it's complicated and requires a lot of thought to come to a reasonable answer. I'm going to be a year too young to vote in the referendum so I'm not looking to pick a side, just understand and think about.
