I believe I do have a timeline of events that you might find revelatory.
Russ informs him that they cannot perform Ding-Dong! The Witch is Dead and that they have to stick to the original lyrics for Always Look on the Bright Side of Life, but can otherwise accommodate his (largely witch-themed) requests.
Pier Pressure perform their version of Woof, Woof, Woof at the Larmer Tree Festival.
The song is introduced as being “from the diseased mind of the drummer” and features various dog impressions.
In a band meeting, one of the members of Pier Pressure suggests they do a cover of A Nightingale Sang in Berkeley Square. Russ insists that they should do “the famous bit” and gives a short rendition of Woof, Woof, Woof.
After an initial stunned silence, the rest of the band start to laugh at Russ’ insistence that this is how the song goes. Their hilarity grows as Russ sings in a high-pitched voice and explains that it is the nightingale doing dog impressions.
The lead singer resolves that they are doing the song. He dismisses the rest of the band except for Russ, to whom he says: “You and me are writing a song, Jawbone.”
When asked, Russ admits that he is only getting the tattoo because of peer pressure from his band. In fact, he tells her, that is literally the name of the band (although they spell it ‘Pier Pressure’ because of Hastings Pier).
The tattoo artist lets him change this answer so that she is allowed to give him the tattoo, but tells him that she can stop anytime he wants.