Don't skimp on the maternity pads! You will need them, lots of them!!! Get twice as many as you think you might need...you will go through them. Also, get some nice cotton granny pants from M&S, you might need them too!!!
In terms of clothes for yourself, pajamas especially. The ward I was on was extremely boiling hot, so I wound up wearing a tank top for most of my hospital stay. Everyday I was there (I was in for 5 days with my son) my husband took my pajamas home and washed them for me and brought them back clean. Also, everyday he brought me a two liter bottle of frozen water, that was a LIFESAVER!!! You can shower and move around the ward if you need to, so bring slippers or flipflops or whatever you are comfy in. If you are breastfeeding, bring a boppy or bf'ing pillow if you have one. I always bring my own pillows from home as I find they help me sleep. The hospital I was in had bath towels, but this time I think I will probably bring my own. Food...bring some food with you. When I had my son my parents were here and my mother cooked for me each day...but OMG do I love NHS puddings. Yummy!
Lets see, clothes for baby...bring a whole bunch of them, I never used scratch mittens, so its up to you whether or not you want to get some. Bring your usualy toiletries, they will make you feel better, hair dryer if you want to. I say bring whatever makes you feel comfy, it could be a long stay (might not, but could be) and you will want to have everything that you need. Oh, and mobile phone and charger, I plan on texting and photo messaging throughout my labour!

Good luck!!