I've just had an interesting conversation with a lady in their call centre.
We have an old family cottage, pretty much uninhabitable in winter but used by all of my immediate family at different times during the summer. It will be unoccupied on 20 March 2022, but I will still have to fill in the household part of the questionnaire.
Question H14 asks how many vehicles the household has access to.
In the case of my own permanent home, that's easy. I have one car.
But in the case of a holiday cottage that is never rented out commercially, how many cars does the household have access to? I reckon that if I add up all the cars belonging to my family, there must be six or seven. I can't just put none, because while that is true on 20 March, the question is intended to help with road planning etc, so answering none is not going to provide the information the local authority needs - there are 15 holiday cottages in the village which obviously generate traffic and therefore wear and tear on the roads, even though none of the 15 cottages is occupied on 20 March.
So I rang up to find out, and at first the lady (whose first language is not English) completely failed to understand the question. She told me I must tell the truth! But I asked her which version was 'the truth', and eventually she grasped the point of my question, admitted she didn't know, and asked me to hang on while she consulted a higher authority. Finally she came back and said I must enter the total number of cars.
So: census return, one household, no occupants, 7 cars!