Policeman (United Kingdom) sends email with official request to obtain some data to company email address, but doesn't sent the post (original paper version) to the company's postal address. Is that right? I expect that the company must get a paper version or am I not correct?
Emails are legally writing and your receipt triggers the legal obligation that they contain (if any). Assuming that the underlying legislation does not restrict how the request must be served (which it probably doesn't) then email is fine.
That said, while the police can request any information they want, without a court order, they have limited power to compel the production on data.