Things have moved on since my first post. Nick, (of this list) also wanted one and got the same request. His Lady advised him it was probably needed, so he provided info and sent the money for the manifold and postage. As i regularly send documents world wide, I am fully aware of what needs to go on (UK and Isle of Man) customs forms. These all go through the Post Office, so I phoned them for advice. The person I spoke to had no knowledge of such needs, and said NO, don't give your info.
I have a pal who is a recently retired tax advisor of wide experience.so I ran the question past him. He had had a similar problem for stuff from Germany, so made enquiries to the company concerned. It seems it is all related to VAT requirements, and since he is not a VAT registered business, like me, it is strictly NOT required. However he did provide it to ensure he got the stuff. He has since concluded that somebody asking for the info is more likely to be "genuine" (not that I doubted Luca) so he advised me to provide the info. That i did, and a few days ago sent Luca the money. By this time, Nick had already received his manifold. I am still waiting.
One thing I did pick up from some of the stuff Luca sent me, was that much of the new requirements do cite BREXIT as the reason for this amount of detail.
Regards, Les.