I've seen this a couple of times before on Mk5 Escorts. It normally turns out to be a burnt out track in the fusebox.

It could be the ignition switch, and it could also be corrosion in the single bullet connector in the black/red wire that runs near to the battery.

Fusebox is most likely though.

You'll have trouble finding a wiring diagram for an RS2000 as the only ones I know of are in the Ford TIS system. The starting system is the same as the zetec versions I believe so you can probably use a Haynes manual.