Mick,
Unfortunately this conversion has also been noted on this side of the Atlantic. It was written up in the winter 2001 issue of the AFTE (Association of Firearm and Toolmark Examiners) Journal.
Anyone with access to a lathe could muddle through making the requisite chamber inserts. A firing pin could be made with tools no more complex than files. Ditto the requisite fitting to the frame. Hypethetically speaking, as the owner of a well equipped tool and die shop, I'd think that anyone with similar equipment and some degree of skill in working on arms could do a workmanlike conversion in a few hours. An amateur would take a bit more time, but the results wouldn't necessarily be a poor quality job.
I'm truly sorry that I can't have provided a less pessimistic answer for you.
Bob