Hospital appointment ??

So I saw the MW on the 25th feb and have chosen the hospital we want to have our baby(s) in but I'm yet to have a letter from the hospital yet for the datin scan? Any one know how quick it was for them to recieve their letter (I know some/most have an appointment booked their and then but they have to send me a letter) I'm in Morley Leeds and have alleged LGI (Leeds General Infermary)