Great to hear all your views - thank you.
Took the opportunity to try on a Speedmaster Professional (05) in an AD over the weekend.
Really liked the watch - from my limited knowledge of Speedys it does seem a faithful reproduction of the 57 model. Liked the fact that it felt heavy and substantial on the wrist (usually a problem as one of the my other watches is a Panerai) and had a real presence.
Closed caseback and original heselite also works from a historical perspective - but have had a few comments that it can be a scratch magnet?
Looks like it will be the next addition to the collection very soon. Again thanks for all the advice.
Will post some pics when purchased