I went back to work when DS was 5 weeks, he is now 12 weeks. I express 3 times a day, it takes 10-15 mins including washing the pump parts. I get in to work for 8.30, express 4-5oz. I then express again at lunchtime, usually 5oz. I try to express again at 3.30, and usually get 4oz. This means I only take one break out of work time, which I can make up (but usually don't...!). DS usually only has around 6-10 oz while I'm at work, and breastfeeds a lot more when I'm home, the remaining milk goes in the freezer. I'm happy with this reverse cycling, as I get to spend lots of time with him, but I don't sleep a lot. Also, has caused a bit of excess supply which is tough, so i block feed too, and we always get covered in milk, forget muslins, just keep a huge towel by the bed!
We got him on the bottle at 2 weeks, he took it straight away, we were very lucky. He now happily takes the bottle from me, and has been known to have it straight from the fridge! He has never had trouble switching although very much gets comfort from breastfeeding (as any baby does).
There is legislation which means your workplace have the duty to provide you with space to express. My pump has a battery pack so wouldn't need a plug socket. I know people recommend against open system, but I got the medela pump in style. It does the trick, and DS doesn't seem to mind a bit of dust in his milk. Maybe you'd need to do more research on this.
We bought the whole medela kit. It cost loads, but my husband was adamant if he were looking after the baby he wanted it all to work together. The steriliser is ok, and bottle warmer fine, but double the price of everything else on the market!
I get home in the evening, put two bottles in the fridge with the date on (masking tape), and one bottle emptied in a freezer bag. I then wash the bottles I bring home and the ones DH has used in the day, sterilise and pack away for the next day. I only bring the pump home at weekends or if I've been/will be out of the office, otherwise it's locked in my desk.
It has taken so much planning and organisation and I thought about it for months before DS was born. I feel so happy that my boy is able to get breastmilk full time even though I can't be with him always, and I get the hugest sense of fulfilment from it. My husband loves it too as no formula to mix! Good luck Bib!