Per the Blue Suede News (and Rob Lamb - see below) Matthew Seligman played bass at this gig, then Andy Metcalfe took over for subsequent shows.

The Punk Diary (p. 38)
Robyn Hitchcock finds himself fronting a band called Dennis & The Experts. Robyn himself is cast in the lead role as "Dennis," while the "Experts" are Rob Lamb, Andy Metcalf [sic] and Maurice [sic] Windsor. They play a few originals of Robyn's and some covers by artists like Little Feat, Steely Dan and select bits of David Bowie. While punk is screaming on in London, Robyn is stuck in Cambridge playing what he later described as "sedate hippy gibberish." The group would only be a brief stopping place on the way to becoming the Soft Boys, with quite a different style.

I started playing with Robyn towards the end of the summer – the first session at Robyn’s that I noted in my diary was 5th September. We would have been rehearsing in Robyn’s front room. He had an old Hofner guitar with red naugahyde covering. He was very new to playing electric. We did some recording there on the 28 Sep – no idea if any of those old recordings still exist.

I can’t remember when Morris and Matthew came on board – may have been all at the same time… but I do have a note that around the 3rd – 5th of October Matthew gave notice that he had other commitments and couldn’t stick with the band. On 8th Oct I met Andy Meltcalfe, but as noted above I think he had met Morris previously.

Robyn was very into Barrett and Dylan (no surprises) neither of whom were amongst my influences. I was still into a Steely Dan / Little Feat ethos (as were Morris and Andy, but I was probably more dogmatic). I remember arguments about the relative merits of Beefheart (Robyn) and Zappa (me). Critical consensus is probably with Robyn at this point in history.

Notwithstanding the impending bass transition, Dennis and the Experts played their first show on 13th Oct at Corpus Christi college with Matthew on bass. The fact that Corpus was Matthew’s college may have had something to do with it. Fairly sure we did a longish Sister Ray with plenty of feedback to an audience of about 12 people.

Robert L