The cossie ecu's can be used to excellent effect, but if you want to go further it can work out very expensive with addded on bits then remap with every mod etc, ask why a lot of cossie people don't use them, they were good in thier day, well no actually the early were shite in thier day to be fair, but ford were interested in sales nothing else.
Bits are going to become harder to find for these ecu's sensor wise, makers are not going to cater for a tiny market, that is getting smaller.
I would also not just pay for a name, you really need to have a budget, the loom on the zetec can be altered to have the new ecu end on, so saving some money there, assuming you are going to have the car mapped on the rollers, consider who you trust, who is close to you, but if you don't mind travelling location not so important, but go by what the person you use reccomends, as he will know this system very well.
tabetha