You clearly don't know what you're talking about.
As a UK citizen living and working in Germany, if you don't have a UK address and you have been there for more than three years you don't get a vote!
The cut off is ten years after no longer being registered in the UK. As I would be personally affected by the decision I'm very pleased that I'm being allowed to vote.
Since the UK buys more from the other EU countries than they buy from it and the UKs traditional trading partners were dumped by the EU there is absolutely no reason why the UK would be any worse off than it is today. In fact it would tent to be better off as an independent trader on the world market.
First of all: trading won't cease but the terms of trade are likely to change and both sides would suffer. However, the positions are not equal. It's not a brilliant analogy but the sanctions imposed by the EU and Russia on each other after the invasion of Crimea are helpful: EU producers suffered but they are able to look for new markets for their products even at a lower price; Russian consumers have to find new suppliers for what they want. Even without the slump in the oil price it's clear that it's easier to find new markets for good products than new suppliers for banned products. Though you read the odd success story of domestic producers picking up the slack, the sanctions have fuelled inflation in Russia and reduced consumer choice.
The UK is able to finance it's trade deficit by running a current account surplus as a target for investment. Leaving the EU is very likely to reduce this inward investment (because the UK would no longer provide access to the single market) but the trade deficit is likely to grow because German cars and, to a lesser extent French wine, (these are the examples that the Little Englanders tend to spout) cannot be easily replaced but they can find new markets. The result, until a new equilibrium is found, is likely to be a decline in Sterling and UK living standards.
It's difficult to quantify any of this but that it is a clear and obvious risk associated with leaving the single market. It's even more difficult to identify areas where the UK has such desirable products for other case (remember the UK has a trade deficit). Moving the legal and financial services to other countries (say Amsterdam or Dublin for access to the EU) or Hong Kong, Singapore Dubai is easy (and already happening). Although HSBC has just decided to keep its base in London, it's easy to see this decision being reversed. In business terms leaving the EU has lots of potential risks and little clear upside.
But the business side is only part of the argument. Sovereignty would be a reasonable argument if there was that much sovereignty left to gain: the WTO, the UN, the proposed TTIP deal all involve loss of sovereignty.
Then there is democracy and accountability. Sorry, but I don't find the UK parliamentary system particularly democratic when compared with other EU countries and there are no indications of it becoming more so if the UK leaves the UK or is Swiss-style democracy (devolution + referendums) on the agenda?
Within the EU the governments of the member states sill wield lots of power with the national veto. The concessions that Cameron has recently wrong out are testimony to this. The European Commission is no less democratic than any Whitehall department or one of the many quangos that governments love to set up.
But, at the end of the day, my chief motivation for wanting the UK to stay within the EU comes down to the many friends I have throughout Europe and the sense of having possibly overcome the dreadful wars of the 20th century that plagued Europe. My dad's house was bombed int he war and I live in a city that was flattened by British bombs. Talk to anyone from the Warsaw Pact or former Soviet Union and they will tell you much the EU means to them. And, how important it is to keep Britain in it.