This post is going to be somewhat broad brushed, I’m aware there are fine degrees and other issues. I’m also not expecting this to happen,
There are three key policy areas from my point of view, Europe (in-out along with immigration), Austerity and civil liberties (vs security).
Labour is split between a real left wing party that believes austerity as it stands is unnecessary and harmful (Jeremy Corbyn, the unions and a majority of party members) and in the New Labour wing which is the majority in Parliament. They are largely EU positive although some on the left are concerned that it is too much under the control of big business. On civil liberties they have been fairly weak at least since New Labour with a high willingness to favour security over liberty although there are fair numbers who do care about civil liberties.
The SNP are very similar to the Corbyn wing of the Labour party with the obvious exception of their wish for full independence for Scotland.
The Conservatives share a belief in austerity but with varying positions on the extent of public services and spending if the economic times were better. Their instinct is generally to cut taxes before investing in improved services. There is a huge and obvious split on the EU, with a majority of members anti-EU and split roughly in half in Parliament. On civil liberties most lean towards the security side but there are notable exceptions.
The Liberal Democrats are largely grudgingly accepting of austerity, pro EU and lean to the civil liberties side on security issues.
UKIP is obviously anti-EU and anti-immigration, they mostly favour security over civil liberties and I’m not up to date on their economic policy. Farage is very financially
As I write the Labour party is tearing itself apart. MPs have been briefing against Jeremy Corbyn continuously since before he was elected by the membership, union members and paying supporters (I’m one of these). The fundamental issue is whether Labour is to be a party of the left, opposing austerity, skeptical of foreign military interventions or to continue the New Labour direction of aiming for the centre, prioritising victory to then be in position to slightly mitigate the effects of globalisation and rising inequality rather than attempt to achieve true social justice.
Imagined Alternative structure
In my personal view there needs to a party articulating a true left position, opposing austerity and fighting for true social justice. This is critical for several reasons even if it is hard or impossible for such a party to win a majority as without it the other parties are pulled relentlessly to the right. Without a party holding a realistic leftwing position there is no centre for the New Labour type parties to triangulate themselves to, and the risk is that the Conservatives move further right to distinguish and differentiate themselves. It is also essential that there is a party prepared to stand up and argue for the marginalised, whether those on benefits, refugees or other migrants.
Given all that I think that a more natural arrangement of parties would be for the Labour party to be Corbyn’s and the membership’s left wing party fighting for disadvantaged, for greater equality and an end to austerity. I can imagine it cooperating closely on many issues with the SNP, the Greens and Plaid Cymru.
The Blairite, New Labour wing has more in common with much of the Conservative party. I feel that a centre-right (although they would think themselves the party of the centre) party could be formed; lets call it the Popular Party. I’m picturing it taking maybe 150 of the current Labour MPs and 100 Conservatives. I could imagine it becoming the official opposition, possibly in a highly pro-EU stance working with the Liberal Democrats. If it didn’t oppose Brexit it would push for a close relationship even if some element of free movement was required.
Then comes the bulk of the Conservatives, largely anti-EU, very keen on privatisation and business deregulation. It would probably subsume many of the non-racist elements of UKIP.
Now while this may better fit the political views across the country and Parliament than the current status the first past the post electoral system acts against it and major party realignments are rare and usually harmful to the parties involved. Having said that anything seems possible at the moment and I feel that there has to be a split in the Labour Party. Whether the Conservatives also split may depend on how unpopular their next leader.