Hello again, and thanks for your assistance.
I have used MakeMKV to extract the contents of a test DVD - Doctor Who, Spearhead from Space - a 4 part adventure. The result was 4x 1.23GB files - 1 for each part - plus a 5GB file containing all 4 in sequence, and then 4 more files containing some of the DVDs "Special Features". (About 2 of the features were missing.)
Looking at the main feature material (both the individuals and omnibus version), I'd say it is not interlaced after all - it's pretty good considering it was from 1970:
With the specials, some were widescreen modern material, which all looks fine, but there was 1 "archival" piece which Does have interlace issues:
(Have just found how to turn subtitles off, btw.. but am going to have to look at commentary tracks, which every DVD has, cos my HTPC always seems to play the commentary versions if they exist...)
I'll have a look at l33tmeatwad/AMVtool next... I could potentially be happy with 5GB per story... That's less than 1TB for every Doctor Who.... although once you add the special features....