Hi Artful,
Only 4 months late with response.
Whilst I agree with you whole-heartedly re 'Creeping Jane' being fictional I thought we were a long way down the road to identifying original sheet music for 'Buttercup Joe' c1870. Am I to assume you have an earlier date for use of the name?

Also while I'm here we can take back the broadside dates a little further for CJ. It appears to have been printed more and earlier in the N of England. the only London printings I have are Such and Hodges, both relatively late. However Madden has a Swindells of Manchester printing I'd date c1810-1850, and in the Firth collection at Sheffield there is Walker of Durham. It appears in Walker's catalogue for 1839.