books/magazines/mp3/gameboy etc - oh god yes. It's sooooo boring waiting to be discharged and it gives your Dp something to do whilst you're in labour for x amount of hours.
snacks - yes, for you and Dp. I had Ds1 in the evening, and by the time everything was sorted out I had eaten nothing for about 36 hours, but had obviously gone through all the physical effort of giving birth to a 9lb+ baby. I was starving, there was nothing on the ward and all the cafes in the hospital were shut. I have never made that mistake again!
small change - I would say yes for the car park but in most hospitals that actually requires a 2nd mortage instead 
mobile phone - never had a problem using it.
Agree with Scribble, paper pants are ........well, pants really. far better to buy cheap big granny ones from Qs or poundstretchers, They feel more secure, and hold the pads in better, which reminds me....
Maternity pads - uncomfortable and bulky. You're better off getting the highest absorbancy night time pads (with wings), they are a lot more comfortable, and imo work far better.