As far as old episodes of Doctor Who and Blu-Ray, the only one that would benefit is Spearhead from Space, as it's the only one that was shot entirely on film. All the others were shot on video (though recent DVD restorations tend to be from film sources, as the video masters were printed to 16mm film for international distribution), so they can't have higher than SD resolution.
I honestly don't remember whether Spearhead was shot on 16 or 35mm film. I'd like to know, though.