I went back to work with dd 4 days a week at 6months and with ds full time at 9 months, I expressed both times, I used to feed first thing, we co slept with babies in a cot attached to our bed until at least a year old as it meant I got more sleep but we also got more bed! They both eventually went into their own rooms, it took a while but there was no way I was tackling that until a holiday or something when I had the energy to.
I took a small cool bag, had the pump in a plastic Ziploc bag already sterilsed and snacks, went at break and at lunch for the first month or so and eventually managed to get to do it just at break and then not at all. I popped the milk straight into the fridge with an icebox in the medical room and then into the cool bag with a freezer pack. When dd went to a childmibder i just took the milk to her when I picked up and she kept It in her freezer. It didn't take long, I just had to ask if I could not be on break duty for a while and sometimes used frees, about 2 people knew I was doing it although I never really hid It, only mentioned if they needed to know and I used the medical room, if it was busy I used our stock cupboard and sometimes the heads pa's office! Bless her she would leave me a chair, make me a coffee and let me get on with it. I did have someone open the door once but it was ok, just shouted it was busy and always sat with my back to the door and a muslin handy just in case.
You'll be fine, just ask, they have to accommodate you, I just told our site manager type bloke I was going to be doing It, he got a bit flustered and just agreed to whatever I needed. In fact I didn't do break duty for the rest of the year even though I could have, bonus 
Oh and I've had two horrific sleepers, was awful I won't lie but it doesn't last forever really you'll be ok. I still feed ds before bed, he's just given up the morning feed but he's boob obsessed. My supply settled right down after a few months. Things that helped were having a photo with me when pumping, took my phone to read etc so I still got a break, dh had to help in the morning getting us so up and out the door. In fact you need to tell him to help, just as much his responsibility as yours that your baby gets fed/sleeps/is happy!