Don't know what the procedure is at Manchester, but at Gatwick any lost property we are given is put into a safe in the office provided by the airport Lost Property. They come and empty it about 3 times a week, sign for the items they collect and take them away.
Did the crew get a signature from the Servisair agent who took the lost property? We are encouraged not to take any lost property unless we and the crew member both sign a form to confirm what is being handed to who. When we put the item in the safe, we sign another form and get that countersigned, so there is always a paper trail to follow for any valuables.