well admittedly it's a long time since I saw the DVD but I remember it being quite dull looking, with poor detail and some obvious signs of wear.
here is a review of the Mill Creek blu which I believe uses the same elements. They might have been ok for standard def but as you can see from the screen grabs they are not great rendered in HD. There is the caveat of course that Mill Creek are shit at transfers and I'd expect PH to do a much better job with the same elements if that is all they have to work with.
Hammer Film Double Feature - Revenge of Frankenstein & The Curse of the Mummy's Tomb Blu-ray