Byelaws to which section 236 above applies may provide that persons contravening the byelaws shall be liable on summary conviction to a fine not exceeding such sum as may be fixed by the enactment conferring the power to make the byelaws, or, if no sum is so fixed, the sum of £20, and in the case of a continuing offence a further fine not exceeding such sum as may be fixed as aforesaid, or, if no sum is so fixed, the sum of £5 for each day during which the offence continues after conviction thereof.