I have in front of me a copy of Autocar July 11,1952 about this car written by R.Brock with the title:Special bodied Healey"
He writes :"When the chassis had been arrived I immediately bent up and welded the structures in the shape desired"
My conclusion after reading the article that the car was built by R.Brock himself and most probably in England.
On ebay I found a collage of photos of the construction of the Healey PPD 224.