Have a look on the nhs website for the hospital you are going to. they will have a list of things as some hospitals provide nappies and other bits and some don't.
if it helps I've packed 3 packs of thick maternity pads, 1 pack of breast pads, 3 dark nightdresses, 2 pairs of joggers that i can wear as trousers or with nightdresses, 10 pairs of granny style cotton pants, 2 bras, jeans, 2 day tops, slippers, light weight dressing gown, wash bag with travel size bottles, lipbalm, haribo, lucozade, & phone charger. for the baby I've got a pack of wipes, 12 nappies, a little teddy, 4 muslin, 2 hats, 2 pairs of socks, scratch mits, 3 short sleeved body suits/vests, 3 long sleeved body suits, a wool cardigan & a small blanket.
A friend gave me a great tip which was to take a separate wash bag and pack it with 3 maternity pads, change of underwear, small pack of moist tissue paper & couple of breast pads she said it saved her digging these things out if she needed to quickly change her pad or had people visiting her when on the ward.