I used to use the museum supplied HP5 when I was doing archival building photography when I was a curator and the combination of development, printing and paper produced excellent results. That was 20+ years ago and since, using other films, I have never recreated the results with HP5 through my own darkroom, so I have not used it much for 15 years and if I do (its the most readily stocked film in these parts) I am disappointed when compared to Delta 400 or Neopan 400, for example. So, because my equipment, preferred chemicals, paper and enlarger have changed I don't use HP5 by choice, it just doesn't like me any more. If you are struggling with it, don't pursue it, settle on the look from another film that suits your equipment/technique.
It sounds to me, 36cm2, that you have a recognisable result that is a step forwards rather than a set back, stick with it.