(1) If no address is given for service the document may be served by leaving it or posting it at or to —
(a) in the case of a firm or partnership – either —
(i) the principal or last known address of the firm or partnership or any place where the firm or partnership carries on business and which has a real connection with the claim, or
(ii) the usual or last known place of residence of one of the partners;
(b) in the case of an individual – that person's usual or last known place of residence;
(c) in the case of a proprietor of a business – that person's —
(i) usual or last known place of residence, or
(ii) place of business or last known place of business, or
(iii) the business address of any legal practitioner who purports to act for the party in the proceedings.
(2) The provisions of Part 5 and Part 5A may apply to such a document as if it were a claim form.