A person is not to be regarded as carrying on by way of business an activity specified by -

(a) article 25C of the Regulated Activities Order (arranging regulated home purchase plans);

(b) article 53C of that Order (advising on regulated home purchase plans); or

(c) article 64 of that Order (agreeing), so far as relevant to either of the articles mentioned in sub-paragraphs (a) and (b),

unless he carries on the business of engaging in that activity.