I can only echo most of what everyone else said on here.
Am I the only person who took earplugs in
Definitely snacks for during and after the birth. It's madness that they push breastfeeding but aren't prepared to feed you the gigantuous amounts of food you need.
I remember our antenatal teacher told us to tick everything we were allowed to on our meal request form, even if you weren't going to eat it in one sitting. I stashed things away and can remember eating a packet of mini jammy dodgers at 3am one morning as my new dd suckled away.
Definitely take a pillow. Don't worry how silly you'll feel (get DH to carry it) when you arrive with a pillow tucked under your arm. The hospital pillows are wrapped in plastic below the pillow case and they make you sweat. Also, when you lean on them, the air seeps out of the plastic and smells of old men's breath!
If you have no reason to suspect you're having a large baby, take some babygrows that are newborn size. I took only 0-3 months and my dd was 6lb 5oz and swamped by the babygrows. (It could have gone any way - my DH was 10lb 10 when he was born, I was 6lb 6)
I am someone who had leaky boobs from the minute I was in labour so take loads of breastpads.
And like everyone else has said, you'll need way more maternity pads than you could imagine.
I bought mothercare nighties that button down part way and found them crap. Perhaps I have low hanging boobs or something but when I unbuttoned it and tried to latch my dd on, she got a mouthful of nightie, I couldn't get the nightie out of the way. I felt better off in PJ trousers with a t-shirt on top, which I lifted up.