from the mid 60s to the mid 70s there are about a hundred billion awesome english folk rock albums across the whole spectrum from very trad to a more modern folk rock sound. most similar to ISB I can think of atm would be stuff like:
Tyrannosaurus Rex's first few albums before they turned into T Rex
Dando Shaft - s/t
John Renbourne Group - John Barleycorn
some early Fairport, Pentangle and Steeleye, obviously
The Sallyangie - Children of the Sun
>>127065717
thats really good and they have a v nice s/t album too
and also look at this old thread for wider recs
https://desuarchive.org/mu/thread/124273498/