I just spoke to Colin Brown (who's on here, or at least was - can't find him) and he remembers visiting it regularly. According to him it was well run with friendly staff, stocking a broad range of current and back catalogue with strong jazz funk and "Essex" type soul content, but not so much rare soul. The staff would hunt stuff down if asked, though.
The record shop issued their own records into the 1970s - all genres. They also owned Stage One studios that were attached / nearby and run by John Bassett presumably a relative. John Bassett was also a semi professional guitar player. It's likely that Jesse Green who was London based used the studio for the recording, The studio was where Depeche Mode cut their first records.
The shop and studio were in Sebert Street in Forest Gate . In the next decade and after my visiting time to Forest Gate, De Underground Records ran a shop and recording studio in Sebert Road which became an important venue in the development of British underground dance music. I wonder if they used the old Stage One premises? (2022)