This article in The Connexion – Time to lobby over expat vote – is urging British expatriates to lobby peers in the House of Lords to extend the right to vote in the referendum to all Britons who live in the EU:

“Allowing all expats to vote for life – abolishing the current 15-year limit – was a Conservative Party manifesto promise, but so far the UK government has not made any promise that the rule will change in time for the referendum.”

“The chairman of the continental branch of the party, Brussels and Europe Liberal Democrats, Giles Goodall, said: “I discussed this with our spokespeople in the Lords and I can confirm that the Lib Dem group will either table or support amendments in the second reading to extend the franchise for the referendum to all British citizens resident in other EU countries, regardless of time spent there, in accordance with our party policy. ”

“Neither the Labour nor Conservative groups in the Lords currently support this policy, but the Lib Dems have undertaken to do so together with crossbenchers [members of no political party].”

Given the Conservative party’s commitment to abolishing the 15-year-rule and the  commitment of Conservative peers such as Lord Norton & Lord Lexden in particular, to abolishing this rule, it would seem more likely that at least in the House of Lords the interests of the Liberal Democrat (101 in total) and Conservative peers (224) would aligne in support for extending the franchise for the EU referendum to all British citizens resident in other EU countries.

http://www.parliament.uk/mps-lords-and-offices/lords/composition-of-the-lords/