Not me. It's not on the top of my "to think about" list.
I've been reading some about it from both sides. It's in our news and newspapers here and there and I've followed most of it. Like all things, it seems to have it's goods and bads but I still haven't found anything on the real reason" Why " Britain is thinking of leaving the E.U. Not being from Britain makes it hard to answer your question but I care as I've been to your country and our two countries have a very strong bond. I'll have to start watching the BBC news more often and see if I can see the "why" of it.
I should think the restrictions (and freedoms!) of the EU would fit uncomfortably for some Brits, so I can understand why the separatist movement is gaining in popularity (Jim Hacker's "British sausages" being a case in point).
It's akin to the Scottish separatists, the Ausrtralian nationalists, the dissolving borders of Yugoslavia, and the disparate ethnic groups living uncomfortably together in places like Iraq, Palestine, Turkey, and parts of Africa. It's natural for traditional nationalities and tribes to prefer their own identity.
On that basis I think separation (the pound vs the euro is already an indicator that the UK prefers her own identity) is of great concern to the British people but concerns the rest of us only marginally, UNLESS it adds to European fiscal instability. If that were to be the case it could be a step toward another GFC which might not be so easy to solve.
The British residents of Gibraltar sure do.
If Britain leaves the EU, there is a good chance Spain will resume their border closings - making it more difficult (and expensive) to get items into that little enclave ... Not to mention making it harder on those who have relatives in Spain. (they could no longer walk/drive across the border to visit - they would have to fly to Britain, then fly back to Spain)
I care, because I live in the UK. I've already made my thoughts known here when a question was asked regarding this topic. I have listened to both the IN and OUT argument. The government spent 9 million of our money on posting us their IN argument. If Brussels makes all our decisions then we are not a democratic country. As a result of that we have no say in firing our politicians. Any decision that is made without the people's say so, is suspect, this decision was made for us over forty years ago. We do not make anything as a country anymore. Not being a part of the EU does not affect our trade, China trades perfectly well just look at their cheap steel that they've imported, businesses do trade not politicians and I've heard this straight from English businesses experiences. The EU trade agreement actually makes trading more difficult, as I've said Russia and China have no problem. We use to have successful fisheries and steel industries, all have gone. We do not make cars anymore, most of our cars are from Germany. Because the EU allow countries to make more food produce then we need, we dump it on the markets and so undercut poorer African countries. If we get OUT we can control our own borders. Then there's TTIP.
If we stay IN all our services will end up privatised. The common man is finding it more and more expensive to stay living in London which is now being owned by the super rich. People say that we will suffer if we leave, but if we don't there will be no way back, we won't build or make anything anymore and will be beholding to another country. In fact I don't think any country is liking it much in the EU, none are wanting to lose their culture and identity. I listened to a German Conservative man say, you know what happened last time someone tired to have the monopoly on all countries "it became a dictatorship." There is an irony to your question also, when asked most people outside the EU do not even know what it is.