I certainly wouldn't have any problems employing a JAA FI purely on the basis of where they are from.
As long as the ability to communicate is there and you have a good attitude, then there shouldn't be a problem.
With regards to issues of standardisation, this can often be a problem for CFI's no matter where their instructors come from. If the FI is willing to go through the process of learning exactly the way we teach at the school and the procedures expected, then again there shouldn't be too many problems.
Personally I would supervise a new instructor very carefully anyway, so hopefully we can find any problems at an early stage.
I believe there are a couple of non uk chaps up at Tayside in Dundee, maybe they could be of use? I don't think there has been any particular problems faced by them.