We got MVHR as a retrofit and the results are wonderful. The one we got is Dutch (it seems to be standard in Holland). There are no joins in the ducts, single runs, wide turns, so no corners. The ducting is smooth on the inside with an antibacterial coating. Apparently, it shouldn't need cleaning but if it does, there is a brush thingy that fits the shape of the ducts.
We got it fitted by a local guy (who I used to work with). It's been in for 18 months - clean filters every 3 months; replace after a year. Not sure whether to post the name here, but if you want it, let me know.
can you PM me the details too!