Ever had one of those times where the harder you try, it just gets harder?
I took another look at Ruston again tonight and just decided to try a LH instead of the RH turnout. Well it snapped into place (I had to snip a bit off the rails) and then I just drug the three tracks closer to the fascia and viola! everything lined up.
The tangent behind the turnout is straight enough to uncouple easily.
Time to move onto the next project...