The UK disenfranchises expatriates who have lived abroad for 15 years or more. This policy has just been upheld by the ECHR. It seems reasonable to me.
To pick on some features cited in the story, as evidence of a close relationship with the UK, I don't see that having family in the UK or a UK bank account entitles one to a vote, or else many foreigners (who don't get to vote and probably shouldn't) would qualify for the franchise. Nor do I see why receipt of a British state pension should bring further entitlements, such as the franchise. Presumably the point is that this entitlement was accrued through years of contributions to Britain, but the veteran in question had the vote during those years of contribution. If he now no longer contributes to Britain, then still receiving a pension would seem more than enough - why should he get the vote as well?
Territory seems a pretty good basis for the franchise, since it is those within a territory who are primarily addressed and bound by the laws (though there are problems here with migration). If this is so, perhaps expatriates ought to be disenfranchised sooner. After all, if they're that close to the UK, why have they been living abroad for 15 years?