A big thanks to everyone for their replies.
As I say, I don't have the disc, but my first thought was that the 'grain' he mentions on the DVD may actually be video noise (on oft-made error).
I know the film has been shown theatrically in the UK recently to promote the Blu-ray Disc, and every PnP fan I know who has seen it says it looks wonderful - they also note that Optimum's logo comes up at the start, so it's clearly the same version.
I think that Thelma Schoonmaker-Powell (Michael Powell's widow and Scorsese's editor) introduced one of the showings and commented on how good it looked.
Of course, plenty can go wrong in the stages between making a print for a limited cinema release and transferring to BD, but I would imagine Optimum would try to get the BD looking as close to the film as possible. This is not action blockbuster fanboy fare, and I don't see why they'd have felt it necessary to de-grain it in the first place.
It certainly looks like Optimum 1 Tooze 0.
Steve W
ps. It has been noted that GT frequently gives poor(er) reviews to the UK releases of Powell & Pressburger films (and those by others), almost always preferring the American editions.
On one occasion he compared the two, but posted screen caps which were smaller for the UK release than the US one. Once blown up it was pointed out that they looked absolutely identical. He then said they looked different in motion and referred to the higher bitrate.
SW