What did I do today......I planned to put in the dash and all the other components in underneath, I even sort the help of a tall gentleman from the east.
So what happened.......absolutely nothing in the end, everything is back in the "storage" boxes.
Moral of the story, check the heater core is the right size after being re-cored....because 5mm makes a hell of a lot of difference.....FFS & rant over.
*Edit: The core itself is technically the correct length, but the two sections where the end tanks are held are slightly thicker & the edges are 3mm higher, so core doesn't sit as nicely inside the heater box, and the metal brace also sits higher