Our hospital doesn't give us formula, we have to bring in 2 bottles, formula and a bottle brush. We're not meant to bring ready made formula and they also don't make the bottles up for us, they want new mum's to learn how to do it while they're there so they're prepared for when they're discharged.
Eventually you're probably going to need bottles anyway as there will come a time that you'll need to express if you want an hour to yourself. Obviously some choose not to express at all but if there's times that you know you'll be away from baby then it's worth having bottles and a sterilizer anyway.
Is your mum going to be your birthing partner? You could either buy formula before hand and leave it in her car or with someone else who'll be your main visitor. Alternatively you can not buy any and wait and see what happens, send your birthing partner out for some if you find you can't do it or decide that you don't want to. I'd personally avoid having it on the ward with you though, you'll only be tempted if he/she doesn't latch on straight away and you might regret not giving it a good go if you gave in. xx