Ah, now isn't that a can of worms.
How are we to decide where the centre of the UK is? Is it the furthest point from the borders (e.g. coasts)? Do you include the various offshore islands or not?
This is either going to be the station closest to Meriden in Warks (Hampden-in-Arden, just 2.21 miles away), which is held to be the location furthest from the coast, or the rival location of the Midland Oak also in Warks (Leamington Spa, 1.08 miles away). Alternatively, if you are looking for the place closest to the centre of a 2-dimensional map of the UK, it could be the station nearest to Dunsop Bridge in Lancs (Bentham, 7.93 miles away) if you are including the various offshore islands, or the station closest to Whalley (Whalley itself) if you are not.
Take your pick.
O L Leigh