I just got the design stage SAP report. Rather shocked at the predicted energy rating of C despite it being a build with high insulation, triple glazing, good airtightness , etc. So I read through the calculation worksheets to discover a load of errors. U values higher than the MBC thermal modelling that I sent them, MVHR completely ignored, generic oversized ASHP used, wrong building dimensions (like 30% greater floor areas and storey heights!).
Entering the correct ASHP alone has dramatically improved the results and I have insisted they redo the whole report using the information I provided.
Very poor effort. I suggest checking any report or calc you receive and don't be afraid to question and push back if it looks wrong to you. We pay good money for services like these.