from what ive been told, power fc's are getting really hard to come by now days, especially in good condition.
there are much better aftermarket ecu's and piggy backs than pfc's now anyway. id highly recommend Nistune if its a fairly mildly modified car.
as for workshops, Mercury motorsport in Wilston do great things, have been going there for about 6 or so years now
EDIT- just read your post properly.. you already have a pfc. call mercury and ask them about prices.