Check with the hospital what is provided it varies so much. Your midwife should help you with a list. The first time I was in they provided nappies and pads etc. The second time (same place) they expected me to have brought my own?
They usually provide pads (for mum) these are huge thick ones, they are softer than thinner always type pads but if you don't have stitches you may prefer a thinner night-time style pad.
Don't take those disposible pants mothercare do, they don't fit well and are the last thing you want to wear when a bit sensistive. I bought packs of cheap pants I could throw away if stained.
If a c-section is likely get some huge granny pants, you will want a waist band that comes up to your belly button above the scar, I sent hubby who didn't quite know what I meant by big pants.
If a c-section you will be in about 5-7 days take plenty pants etc so your not waiting for hubby to take them home and wash them.
Make sure your nighties are suitable for feeding if breast feeding, you don't want to have to pull up your nightie right up to feed during visiting.
Don't worry about over packing if hubby or partner is there to carry the bag. You will leak, dribble and sweat, as will baby.
I also took small cartons of fresh orange to ease constipation and diluting juice as you will want to drink a lot in the warm ward and water gets boring.