The actual state of your home is irrelevant when applying for BUS. The two criteria are that loft insulation and/or cavity wall insulation are not advised.
By those criterea, if you have a solid walled flat roofed house you are guaranteed a grant. That isn’t to say that the house is in any way suitable but the government is fixated on EPC.
The government thinking seems to be “we specified the rules for EPC, therefore it is perfect”. This despite the fact that there is a parliamentary review in process.
As regards whether your house is suitable, did BG do any energy loss calculations? You need the heat loss of the house to be less than or equal the capacity of an example heat pump in its optimum COP range.
In 2007 I had a very detailed heat loss calculation done on my house by NIBE. Their calculation was 8kW. 8kW heat pumps are available but I wasn’t happy with the result and continued working on the house until Daikin calculated 6kW heat loss. At that time the BUS was available and I decided to bite the bullet and go ahead. Otherwise I would have kept on going until a point was reached where the next stage in retrofit costs more than the heat pump.
Three lots of insulation are recommended in the EPC. Is recommended different from advised?
If I can’t ignore recommendations then I need to address
a) If room in roof insulation is different from loft insulation then again I can ignore it. But EPC assessor wanted to see Building Control completion certificate, which I could not provide, so had to assume uninsulated, hence the recommendation for insulation. I was asking for advice on what other proof I could provide.
b) if cavity wall insulation excludes a hard to fill cavity then again I can ignore this recommmendation. Otherwise the cost of EWI insulation of the gable wall will likely exceed the cost of the heat pump.
c) having reread the eligibility criteria again, I see that underfloor insulation is not mentioned, so the fact that I am having that done is irrelevant,
So it looks like I need to check 1) whether room-in-roof insulation is included in loft insulation, and 2) whether insulating a hard to fill cavity is included in cavity wall insulation.
Yes, BG did room by room heat loss calculations. The whole house heat loss was calculated as 7457kw. They didn’t give me the room by room calculations, but they did give me a list of replacement and additional radiators, type and sized for 50 degrees flow temp and design temp of 20 degrees (target temp currently is 19 degrees. And said they would install an 8kWh heat pump.
I’ll soon be at the stage where doing more retrofit will cost more than a heat pump and I’ll still be burning gas 
Recommended/advised: Sorry, my poor wording.
Beware EWI over an unfilled cavity. Unless the cavity is sealed the air in it will warm, migrate out of the cavity and disappear taking your heat with it. This is why EWI is only advised on solid or filled walls.
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Update in case of interest to others:
Refreshed the HeatGeek web page today and the warning about the EPC had disappeared!
Some digging around finally led me to the latest Ofgem Boiler Upgrade Scheme installer guidance which states
3.37. Properties with EPCs containing no recommendations for loft or cavity wall insulation
meet the eligibility requirements for insulation. EPCs with other recommendations, including
those outlined in paragraphs 3.38 and 3.39 are eligible. Please note installers should ensure
that systems installed are appropriately sized to address heat loss where the EPC has other
recommendations.
3.38. Room-in-roof insulation is deemed distinct from loft insulation, and therefore
recommendations for the installation of room-in-roof insulation do not cause a property to be
ineligible for a BUS voucher.
3.39. Likewise, solid wall insulation, (internal or external,) is distinct from cavity wall
insulation. Properties with recommendations for solid wall or internal wall insulation can still
be eligible for a BUS voucher, provided they meet all other eligibility requirements.
So for now the strategy to start with underfloor insulation, alongside airtightness work and ventilation, and some bigger radiators seems ok.
You probably have a good idea about the sizes of radiators you need. If in doubt oversize. You can reduce the heat from an oversized radiator but cannot get more than its maximum from an undersized one. Try running your boiler at as low a temperature as possible to determine the adequacy of the radiators for a fuel pump.