Pray to the gods and worship the goods...
Very rare and I haven't been able to find a sample, but a song from this demo - "The Crucifixion of Possessions" - was previously recorded and included on Crass Records compilation Bullshit Detector Vol 3.
The Bullshit Detector insert says "Recorded 1.4.83 at Slaphead Studios" which was the Kak demo session. Kak was recorded with the same lineup and released a few weeks before Unpopular Yawns.
Note, the above photo is early ND (1985) but not early enough to reflect the lineup on this demo, which was:
Nicholas "Nik Napalm" Bullen (Vocals), Miles "Rat" Ratledge (Drums), Finbar Quinn (Bass), Graham "Robbo" Robertson (Guitars).