First past the post is weird, 2024 edition

Some quick background for non-UK readers: the UK is having a general election on 4th July. In just about every constituency in England, there are realistically only three parties that might win; going from most left wing to most right wing, these are the Labour party, the Liberal Democrats and the Conservative party. The almost certain result of the election is that Labour will win the most seats, followed by the Conservatives, and very likely with a overall majority; betting odds imply something about a 5% chance of no overall majority.

My personal preference would be for a Liberal Democrat government, followed by Labour and then, as a distant third, the Conservatives. Given that I'm not completely stupid, I recognise a Liberal Democrat majority government isn't going to happen - but given a fixed number of seats for the Liberal Democrats, what would give them the largest say in any potential coalition is Labour being a little bit short of an overall majority. Now, given that I live in what is nominally at least a Labour-Conservative marginal seat (it was Labour from 1997-2005, Conservative in 2010 and 2015, before being Labour in 2017 and Conservative again in 2019), how should I vote?

I think there is a reasonable argument that I should vote Conservative, my least favoured party, as this has the chance of reducing the size of the Labour bloc, and thus giving the Liberal Democrats a greater say. This is... odd. I appreciate "first past the post induces seemingly irrational behaviour" isn't a new insight in any way, but it's the first time it's happened to me in my life.

Practically, I suspect Labour will win easily here which means I can vote Liberal Democrat without much bearing on the world.