The units should be pretty easy to shrink. What are you going to do about the doors though?
I had to do this to a unit a couple of years back (the builder calming informed up as he completed the job that the w.m. space wasn't big enough for a w.m.) and it occurred to me that there should be an opening for a competent joiner to offer a customisation service doing things like this - much as some clothes places offer an alteration service. My unit door was basically a frame round a hardboard panel and careful cutting and reassembly produced a door as good as the original.