A person is not to be regarded as carrying on by way of business an activity of the kind specified by -
(a) article 25A of the Regulated Activities Order (arranging regulated mortgage contracts);
(b) article 53A of that Order (advising on regulated mortgage contracts); or
(c) article 64 of that Order (agreeing), so far as relevant to any of the articles mentioned in sub-paragraphs (a) and (b), unless he carries on the business of engaging in that activity.