The base didn't split. Though thinking about it, in some respects I'm talking a load of loblocks. The Carltons had the brilliant spring-loaded flat metal flappy things that folded forward with the seat and forced it down flat without the need to fold the base forward, so I did have what I needed, and thinking about it, it came in handy loads! My memory's obviously failing....
What do you mean by no vertical bits behind the front seat? As in the base not needing to go up? Probably a bit like the Carltons then. I remember someone saying that the top half of the *front* seats in Omegas actually folded forwards as well, meaning you could get something as long as from the dash to the back of the boot loadspace in there. Though I've never personally seen this on any Omega I've been in.