Just a quick update on this board.

I'm keen to test out the repair but need to sort a few other issues first.

There were a couple of transistors missing/damaged on the board as well as an obviously broken capacitor, so all of these were replaced.

Next I removed the existing sockets for the PIA chips as they looked a little worse for wear.  The solder pads were all cleaned and sanded lightly.

The 40 pin interconnect header was the next to go.  These things are a real pain to remove! 
First I cut and removed the plastic surrounds piece by piece, before desoldering and removing the pins individually.

The last picture shows close up, exactly why these connectors must be replaced.