25.—(1) For the purpose of these Regulation the address of the principal office of a company registered outside the United Kingdom or of a partnership carrying on business outside the United Kingdom is the address of its principal office within the United Kingdom.
(2) Without prejudice to section 24 of the Interpretation Act (Northern Ireland) 1954, if a person to be served under these Regulations with any document has specified to the Department an address within the United Kingdom (other than an address determined under paragraph (1)) as the one at which he or someone on his behalf will accept documents of the same description as that document, the address so specified shall also be treated as his usual address for the purposes of these Regulations.