As Margie pointed out and Howard Turpin from Learning Services spotted, the Unknown Sculpture can be found in Southport and thanks to the scary wonders of Google Street View we can even see it!

Update: I should have thought to look in Fiona Montgomery’s book earlier as it tells us (almost) everything we want to know:

The Eternal Struggle by Dan Manning is one of the best known of the Edge Hill sculptures. In the tradition of Henry Moore it was originally on show at the Crystal Palace. Constructed from preformed concrete, at first sight it seems to be two separate parts, closer inspection reveals that it is two separate parts, but linked. This gave the title ‘Eternal Struggle’ and, in a burst of irony (?), is was located outside the Chief Executive’s window!