You will often find a lot of companies are reluctant to touch engine which have been built by others, as it can be a big can of worms for them and i can imagine the majority would prefer to sell you a new engine built by them.
Obviously you're unable to go back to Chris and I believe you've been to see Ollie Clarke at some point last year?
Dunnell Engines in Suffolk have a good history with building strong and quick Zetec engines.
Scholar Engines, again in Suffolk, also have a good history with building Zetec engines.
Harris Performance Engines, in Kent, built a 2.0 litre Zetec for one of my work colleagues for his mk2 Escort.