Where a notice was defectively served under section 42 of the Leasehold Reform, Housing and Urban Development Act 1993 and the benefit of the notice was assigned to a purchaser, the landlord progressed negotiations with the purchaser on a without prejudice basis in any event, but the notice was then deemed withdrawn as the lease was not agreed within six months, when can the assignee serve a new notice, ie two years from completion of the assignment, or from registration, or one year after the deemed withdrawal?