At a guess they would of used a custom loom and just connected the parts they wanted to existing wiring etc I don't think a ford would of cut the loom out as iam sure the focus ecu controls everything on the car like interior lights etc as well as the engine iam not 100 % sure but I remember doing a car for Ian where we just tapped into the coil
Etc to get the car working.
I think the car kept cutting out as the immobiliser was kicking in but we finally got our head around it after a few hours.
Get a specialist to look at it but I would pay the £300 odd quid to get it unlocked as I still think it would be cheaper.
Have you tried life racing as I think they used to be pectel engineers before starting life racing so they may have contacts .
Who have you tried cosworth electronics?

Cheers paul