What you should take if going into hospital in the UK is:
*Your glasses
*Mobile phone
*Any medication you're on (both prescribed and over the counter)
*Lip salve, tissues, hand wipes, moisturiser
*Toiletries, nightclothes, dressing gown and slippers
*Light clothing to get dressed in if you're going to be in for a few days
*Cordial, fruit, or light snacks if you usually eat between meals
*Enough money or debit card to pay for TV (expensive)
*Something to pass the time - tablet, puzzle book, novel, game, magazine
*Usual advice is not to take in valuables or lots of money, although you will have a bedside locker and staff will sometimes agree to keep things safe for you
My guess is that, from what you've said, you will likely only be in for one or two nights so don't worry if you forget something. There is usually a little shop on site that sells everything obvious that you might need.