EVERY so often, something happens to remind you just how distant England is becoming.

Whatever happens in the Scottish independence referendum, the two countries are growing further and faster apart. And this will only accelerate as we approach 2014.

It was Nigel Farage of the UK Independence Party (Ukip) celebrating his defeat of the Tories in Eastleigh that brought this home. There he was, fulminating against the EU, immigration, gay marriage and wind farms – in that order. Between them, Ukip and the Conservative Party – two organisations that barely register in Scotland – had more than half of the vote in this crucial by-election. The centre of gravity of English politics is pulling dramatically to the right as issues such as immigration and Europe have come to dominate politics south of the Border.

And this is also affecting Labour. Explaining her party's dismal fourth place in Eastleigh, Angela Eagle MP on BBC One's Question Time mentioned immigration as Labour's priority issue. Can you imagine a Labour politician in Scotland saying that? Actually, given the party's ideological discombobulation north of the Border, I suppose anything is possible. But I just can't imagine Johann Lamont raising immigration along with the "something for nothing society" as key areas of Labour policy.

Immigration is simply not an issue in Scotland. Or rather it is, but only because increasingly restrictive UK policies are choking off the flow of migrants we need to cope with our ageing population. As the head of the Equality Commission, Trevor Phillips, put it in his Bob McLean lecture on Friday: "Frankly, unless we can find a way of putting three-year-olds in front of computer terminals, Scotland will need to import skills and labour for decades to come." He went on to lament the "unpleasant populist" drift of politics in Westminster. Now, Phillips is no nationalist and was supposed to be giving a speech supporting Better Together, but ended up putting his finger on a key difference between the constitutional debate here and in England. There is no ethnic or communal dimension to it, whereas in England, there is a very powerful underlying racial and ethnic debate going on.

Similarly with Farage's other hate figure: the European Union. In Scotland, the argument is all about how independence might endanger Scottish membership of Europe. In fact, it isn't even about that, it is about how Scotland might have to spend just 18 months out of the EU while it renegotiates membership. The possibility Scotland might actually leave Europe is never mentioned because it is considered politically unthinkable. This is actually quite odd because many small independent countries like Iceland and Norway do well outside the EU, and you might think there would be at least some debate here about the possibility of independence from Europe. But no – the consensus here is that Scotland has no real future outside Europe.

CONTRAST this with England where politics is going to be dominated by the possibility of Britain pulling out of Europe in the referendum in 2016/17. The gains made by Ukip will force David Cameron's Conservatives to move even further to the right on Europe, and on immigration, if they are to combat the threat from a party that is small, but could come second in a large number of marginal seats and rob the Tories of victory. It is beginning to look as if Britain is on a path which will lead at the very least to a profound change in its relationship with the EU, or its formal departure. Britain is becoming ever more semi-detached, and eventually Europe will tire of accommodating Anglo-Saxon exceptionalism

I'm not being complacent. I'm sure many people in Scotland have concerns about the EU, not least in fishing constituencies. And I have no illusions about Scots being in some way immune to prejudice, either against homosexual marriage or immigrants. There are still homophobes around. We know for certain there are a lot of people who don't like wind farms. But looking at the socio-political make-up of Scotland – with its two main parties competing for the centre left and the Conservatives almost irrelevant – it is hard to see how the countries that share the UK can be said to share the same political culture.

This divide is going to provide the backdrop to the Scottish referendum campaign over the next 18 months. The SNP are on the case, of course, and say the only way to protect Scotland from Tory austerity is by voting Yes to independence. But prominent figures in the UK Labour Party, like shadow foreign secretary Douglas Alexander, are also aware of the danger – as he sees it – of Scotland slip-sliding to independence because of unease at politics south of the Border, and the understandable fear among Scottish voters that a No vote could leave Scotland exposed to it.

Alexander is calling for the creation of a National Convention, a cross-party body based on initiatives to debate and fashion a new form of radical devolution for Scotland after 2014. He believes it is no longer enough just telling Scots they're better off in Britain when the UK has lost its credit rating, is heading for the exit in Europe, and is ruled by a political party – the Conservatives – which has little representation in Scotland and are pursuing increasingly right-wing policies.

Unionists need to provide guarantees, not just that they will deliver on more powers, but that Holyrood can still insulate Scotland from the tide of right-wing Conservatism in England. This is deadly serious for Labour because there is little chance of their forming a government in Westminster if they lose their contingent of MPs from Scotland. The question is: can Unionists craft a new form of devolution to meet these requirements? Could Scotland have its own welfare and immigration policies? Its own taxation policies to fashion a Scotland less committed to austerity? Is it possible to pay for this social democratic Scotland without North Sea oil? And what about Europe – how could Scotland stay in if England pulls out?

Nationalists will scorn Alexander's ideas as just another way of distracting Scotland from independence, by making "promises, promises" that will never be honoured. But as this column has argued before, if there is a No vote, the SNP is still going to be the government of Scotland, and it's going to have to have an idea of how it will show its continuous relevance. This is not defeatism, it is realism. If the SNP doesn't hold on to the centre ground in Scotland – the majority of Scots who want a kind of federalism rather than full independence – then it will lose it to the Unionists. You can still support independence and want a better Scotland short of it.

We are going to see some remarkable political changes in the next 18 months and both the Yes and No campaigns will need their wits about them to deal with the Farage factor.