Here are some in a letter to the Grauniad, signed by many of the usual suspects (though they are not, thankfully, calling for that referendum).
1. We have 3m jobs exporting to the EU but it has 4.5m jobs exporting to us. We are its largest client. 2. The EU has free-trade agreements with 63 countries worldwide and another 63 on the way, so why not with us, on satisfactory terms? 3. Switzerland, not in the EU, exports three times more per capita to the EU than we do. 4. Only 9% of our GDP goes in trade with the EU (in deficit), 11% goes to the rest of the world (in surplus), and 80% stays in our domestic market. Yet Brussels overregulation strangles all 100% of our economy, and handicaps our exports to the countries of the future. Leaving the EU would create jobs, and restore our democracy.While I have some reservations about the last sentence (leaving the EU will not automatically do either of those things), the four cardinal points made in the letter are not only true but are also useful arguments. Mind you, when one produces them, one still has to deal with the dubious facial expression and a muttered "yes, of course, but even so" from a lot of people.