Has anyone managed to retro fit cruise control to a Focus?

Its a 2005 1.6 TDCi C-Max Zetec.

I do loads of motorway miles and would love cruise control, unfourtunately I couldn't afford a Ghia model whcih has cruise already.

I don't really want an aftermarket system, I'd rather fit OE Ford buttons like a Ghia. Any ideas how I would go about doing this and whats involved.

Or has anyone got wiring diagrams/parts schematics?

Cheers!