I *think* a handful of Companion Chronicles have subscription-only extended extras, but not sure which ones.
Here are the extras you get from individual purchases that I know of:
The Dalek Occupation of Winter - extended extras
The Companion Chronicles: The Second Doctor Vol 2 - extended extras, two music suites
The Martian Invasion of Earth - 1st draft script, final script, music suite, extras
The Prisoner Vol 2 - scripts, score, extended extras
The Island of Dr Moreau - extended extras
The Companion Chronicles: The First Doctor Vol 2 - scripts, music suite
Cold Fusion - extended extras
The Companion Chronicles: The Second Doctor Vol 1 - scripts, music suite
The Two Masters - extras (CD version has no extras due to lack of room)
The Tenth Doctor Adventures Vol 1 - scripts (also with individual CDs, I believe)
Jago & Litefoot Series 8 - score and lyrics book
Jago & Litefoot Series 5 - music suite
Voyage to the New World - extras
Echoes of Grey - extended extras