@Fountofwisdom,
Funny thing about Pretenders Chrissie Hynde and their syle of music. Whoever (rock critics) puts them in a niche has them as Punk or New Wave. I think of New Wave, back then, was pretty progressive. I always question Rock music critics and their or industry labels...hmmm?
Oh yes, Incredible String Band. Scottish group, weren't they...sort of described as psychedelic folk and/or World Music?
Talking about ISB reminds me of a group I would consider on my list:
Pentangle. Yes, they are Folk-rock or Jazz-folk, but their music is sure progressive, at least in my mind. John Renbourn and Bert Jansch were incredible. John Renbourn had a few great albums ('Sir John Alot of' ... '68 and
'The Lady and the Unicorn', '70). However this is not progressive but more a mixture of jazz/blues/folk playing alongside a more classical/early music style. However, I digress.
Yes, Suzi Quattro and those leathers ...sigh. Music...oh that was good, too!