There website now seems to include more musicians. My guess is they're a collective who put together a lineup for each gig depending on location and availability, as opposed to simply putting together a scratch band of whoever they can round up. I had hoped to have a chat with them to find out more.

My guess is that you might be able to find someone who would most likely participate in a gig in (say) Stoke-on-Trent, but it seems possible that the lineup may vary from gig to gig even in the same town.

This is of course pure speculation on my part, since the Ship Band have declined to explain themselves - not that they're under any obligation to of course.