(1) Any agreement made before service of notice, under section 8, of the assignment of a receivable between the assignor and the debtor that affects the assignee's rights in respect of that receivable shall be effective as against the assignee, and the assignee shall acquire rights in the assigned receivables, as modified by such agreement.
     (2) Any agreement made, after notice of the assignment between the assignor and the debtor that affects the assignee's rights, shall be ineffective as against the assignee unless,—
         (a) the assignee consents to it; or
         (b) the receivable is not fully earned by performance and either the modification is provided for in the original contract or, in the context of the original contract, a reasonable assignee would consent to the modification.
     (3) Nothing contained in sub-sections (1) and (2) shall affect any right of the assignor or the assignee arising from breach of an agreement between them.