7.—A person who in a street or public place solicits or importunes another person or other persons for the purposes of prostitution shall be guilty of an offence and shall be liable on summary conviction to a fine not exceeding—

(a) £250, in the case of a first conviction,

(b) £500, in the case of a second conviction, or

(c) £500 or to imprisonment for a term not exceeding 4 weeks or to both, in the case of a third or any subsequent conviction.