Here’s an interesting article in The Connexion of August 2015 by Bob Lewis who is currently President of the Franco-British Chamber of Commerce in Paris.
He argues that all British expatriates within the EU should have a vote in the upcoming Referendum on Britain’s continuing membership, even if the 15-year-rule is treated as a separate subject.
However, suggesting to the Prime Minister to “tackle the 15-year rule as a separate subject if you wish, as there are those who oppose giving elected representation to non-resident Britons”, can only apply to those expatriate British citizens living outside the EU.
Those expatriate Britons resident within the EU and, therefore, directly impacted by the outcome of the Referendum on Britain’s continuing membership, can already present this as a valid counter argument for their right to vote.
Votes for Expat Brits blog 
And why should it be limited only to EU-resident British expats? I can see why some people would have this view, but I see no difference. For expats living elsewhere in the world, who will hopefully be able to vote in general elections following the lifting of the ridiculous 15-year rule, those most likely to vote are those who care about the politics of their native country. Just because we might not be directly affected by EU laws at the present time does not mean we are not interested in the future of our nation.
Its a no brainer why in a democracy UK citizens do not have a right to vote / Representation at the UK Gov. Since Westminster woke up to the fact that this planet was getting smaller by virtue of modern communication systems in 1985 / 89 Representation of the Peoples Acts – overseas UK Citizens right to register to vote – here we are 30 years on and the original time limit has even been reduced . Presume since ‘The Lords’ were asked to produce a case for the need to extend the current 15 year rule to life it would affect their pockets on account they get £s for hot air / reports : surveys and the like if DC deigned to make an exception for Brexit Ref. The Political Parties , Elections , Referendum Acts 2000 not only reduced the time limit ( 20 years to 15 years Page 141 Miscelaneous 1 line amendment) but empowers the UK Gov. to make one off amendments to this Act . Its simple but since UK Gov. never learns – remind them when UK Citizens are deprived of EQUAL RIGHTS to Representation they demostrate ( 1968> N.I. one man one vote )
As they say ‘It’s a no-brainer’ – To anyone who has a brain it is plain stark simply obvious. Those who are most affected by the decision of the Referendum must have a voice. Why are the brains of those with the power not active? They are, are they? deliberately stifling the voice of the people?