Here is the situation as of 14 December from DBA forum
A Summary
HMRC have accepted that HVO can be taxed as a rebated fuel with duty and VAT similar to red diesel.
It can be used to heat homes, and by extension heat non-commercial (recreational and residential) boats and be used to provide light and power.
It can be used to propel recreational craft if full duty (and VAT) are paid on the proportion used. The principal issue is price. Directorate of Transport (DfT) have taken the view that under the Renewable Fuel Transport Obligations (RFTO) the issue of Renewable Fuel Transport Certificates (RTFC) (the subsidy) will assume that marinas will only sell HVO at a 60/40 split and the duty is due accordingly - this results in HVO generally being significantly more expensive than red diesel and
Bulk supply of HVO for heating is available at the rebated rates of both VAT and Duty (usually at a minimum drop of 500 litres by tanker but some HVO available in 205 litre drums). Both Crown Oil and New Era Fuels supply HVO for heating.
This position has been agreed by my RYA and IWA colleagues.
The next step needed is to approach all the government departments concerned DEFRA, DfT, HMRC and Department for Business Energy and Industrial Strategy (DBEIS) to achieve a common structure recognising the use of HVO made from waste oil as an appropriate interim solution for reducing pleasure craft emissions, reflecting the existing tax arrangements for red diesel used for propulsion in recreational craft, and confirming the full application of RFTCs.