your daughter has been offered your second choice school but don't worry your DD will automatically go on to the waiting list of your first choice.But if your LA has asked you to write to school in writing to put down your DD's name on your 1st choice waiting list then pls do so(i'm sure you would have done by now coz the waiting list re offers has already been started).
Don't worry about the letter,its just a formality.please accept your 2nd choice and wait for the movements.Your DD's name will be on the wait list until 2017 august.Good luck and hope your DD gets into her 1st choice school.
samk, is your first choice Wallington (I think I saw that you had posted a while back that 'hopefully you would get an offer' from them?)? If so, according to the admissions policy, the waiting list is only maintained 'as is' until the end of December 2016:
4.12 After 31st December in the year of entry the ranked waiting lists will be combined into one list, with equal ranking for all applicants. New applicants will be added onto this list and entry will be
considered under the arrangements for mid-term admission. Parents wishing to remain on the waiting list after this date must apply through the London Borough of Sutton Education Department stating their wish and providing the child’s name, date of birth and the name of their current school. After 31st December in the year of entry, parents whose children are not already on the waiting list but who wish them to be so must apply for mid-term admission through the London Borough of Sutton Education Department.