With DD1 I went back to work and dropped a feed a week, in the weeks preceding. I had to travel for work though and it wasn't an option to keep feeding. We had a nightmare though and she completely refused every type of bottle, cup, formula and BM by the time we were done. Had to give her a lot of cheese!
This time around, with DD2 I'm hoping to do the morning and evening feeds too, and I'm hoping to express one feed per day in the office for a month or so. So one or two feeds a day will be formula. Aiming to be completely weaned by 8/9 months. I go back in 4 weeks so I am now only b-feeding at 7am, formula at 11am, express at 2pm for the 3pm feed, bf at 5.30pm and formula/bf top up at 7.30pm. Basically my DD has been refusing a bottle at 11am drinking 100ml max and waiting until the 3pm feed so I've canned that this week so that she gets used to having a bottle feed during the day.
I've expressed at the office already on a KIT day and used a battery powered pump. It was sooo noisy. Hoping to find somewhere quieter this time around...otherwise I think my embarrassment levels will kill off my good intentions very quickly.
You won't be able to do full feeds on weekends unless you have expressed all week at the times you would have been feeding at. Speaking from experience, most babies prefer to be BF given the choice and it will simply make life difficult for your baby's carer (and upsetting for your baby) on Monday morning.
Will you be relying on public transport to get you home on time to feed? Any chance your office will allow you to do a 9-5 a bit longer than one month or is it just that you know the culture means 9-6 and leaving "early" to feed your baby will meet with raised eyebrows? You know your job, your environment and how important or not it is to you to keep feeding your baby yourself. It's worth looking at American websites for tips as they often return to work at 6 weeks
8-7 is a long day - I think that honestly while you could continue to BF you are going to have to be pretty dedicated to do it. You will need to be up and dressed before feeding the baby (they have a nasty habit of taking their time when you are in a hurry) before you leave. And your baby will be tired by 7pm so potentially you will be BFing your baby to sleep every evening which will make it very difficult for someone else to ever put them down. I know that personally, I'm prepared to do that for a finite period of time, I've made my decision (assuming the baby agrees and falls in with my plans....) and it won't cause me any angst to finish when I have decided to. All I would say is by all means make a plan, but a) your baby might go his/her own way and b) don't beat yourself up if you move to formula sooner than you would have wished.