Hi @jwoodall - I tried to open your file, but it seems that your geometry is not internalised. However, I noticed that you are using the _Masses2zones component.
If of any help, I normally create zones (_createHBzones) from individual surfaces (_createHBsrfs). It takes more time, but I find that I have more control over the model. Image below from a HB workflow I was working on couple of weeks ago. If @mostapha or @chris could propose a faster workaround, I would be glad to know it too.
Also note that you would need to create custom occupancy, equipment & lighting schedules and internal gains in line with CIBSE TM59 (picked this up from your file name).