I have not driven a 3.7 roadster, my 3.0 suffered from rev hang and made driving it unpleasant if not dangerous when approaching roundabouts or junctions, you had to rely on the brakes as the engine held its revs, it's a shame Morgan can't sort out the ecu problems, they seem to be prevalent in quite a few models/engines.
Hope there were no injuries.
I had a series 2 of 2008 with rev hang as well and for this models there was a solution by changing the ECU under warranty one year later. Perhaps MMC has some more spare ECUs regarding this model. It also felt more powerful after the change.