Dave,
I had the HKS R-type fitted by CW. He did a great job a usual.
Things to consider when fitting a FMIC on UK Spec -
It blocks the rad a lot but, I did not have any issues at all for the 2 days I had it, the amb temp on the M6 home was around 25-29 deg C that day and the car was fine but, did not drive at WOT.
The FMIC does obstruct airflow or heat up the airflow to the AC cooler and so, the normal very cold AC was kind of cool ish, somthing I was not aware of before I purchased it so, if you really need a cold AC system then IMO a FMIC is not for you.
The temp probe is affected as per this thread but, I was going to find it and relocate it.
You loose the active spoiler and the front part of the undertray which, is incorporated into the active spoiler but, there is a mod you can do to fix this http://www.mohdparts.com/mohd_bottom_panel/install/index.html not sure if this can be done on the R-type though.
The Auto box cooler which is located in the front passenger side air scoop on the F- bumper has to be removed to allow fitting of the FMIC, not sure of the issues, if any, this causes, I understand this is not on the j-spec.
That's about it, I can not say anything about the performance of it as I did not have it long and did not test it.
HTH m8