Basically they observed (both of us) and tried to get the feeding sorted
They were very supportive of the fact that I wanted to continue breastfeeding and also looked after my post-natal needs (we were on the paed ward, in a side-room where I had a proper bed, and they sent a midwife across from mat to check me over each day). They supplied a pump, helped me to use it and I got into a routine of feeding him and then expressing, (a) to try to get him to take more bm and (b) to up my supply. Was in from Tuesday to Friday.
My memory is a bit hazy (wasn't the easiest of births and I was on medication) but generally I fed him and then expressed whilst someone else tried to give him a cupfeed/bottle of ebm (in hospital). Once home often had to do all three things myself. Don't quite know how I managed it tbh with a toddler running around too, but like anything you get through. DH was fantastic too.
I continued expressing and topping up for about six months (after a while not after every feed) - by now I didn't need to express so much, but carried on to ensure I had enough iykwim. By this point he was on solids and then I continued b/f until he was about 13/14 months.
In theory being at home would have been better, but at least being in hospital meant I could concentrate on the baby (much as I missed my toddler I knew he was being well cared for by my parents). It was also quite restrictive but I had BF my eldest, and was determined to do the same again (aided somewhat by my HV who was great generally, but who insisted on mentioning formula in passing "just in case" on her way out the door)
I must stress though that DS was very sleepy and had dry nappies, therefore imo hospitalisation was correct for us. It would have been foolhardy not to get a 2 lb weightloss checked out (even though he was such a big baby).
This doesn't sound like your experience with your ds2 at all. Hope it all works out ok.