If anyone's interested I managed to purchase a DVD with English subtitles via the following email address: [email protected]
Very helpful (eBay) seller who'll happily answer any questions, arrange payment and delivery.
At request screenshots are also provided.
This was (I think) probably not a commercial DVD release. The movie is currently commercially available on DVD but only in the original Italian language version. The subtitles on this issue are in Mandarin Chinese!
Fortunately, here in the UK, the movie was shown on late night TV (some years ago) in a version with English subtitles and I was able to record it on VHS tape.
I have recently transferred it to DVD myself with good results.
This wonderful European movie still requires an English language subtitled
(commercial) DVD release - but since the recent (inferior) Hollywood remake, I very much doubt if we will ever see it.