I have the same hope as you Andy_B
I bought Mondeo V6 front calipers for 278mm disks - same setup as in Scorpio/Granada Cosworth 2.9 and standard rear Sierra calipers/disks.
When I was calulating results with some brake calculator - it should works
It depends on master cylinder... but there is a hope
I plan to use Omega A master cylinder with 22mm/19mm pistons... smaller for fronts - like in pedalboxes.