Incredibly bureaucratic, if you're used to a slick fast moving operation like M&S, JL will be a shock to the system, even simple requests take an eternity to action.
IT systems are a complete patchwork that has been bought off the peg and are in no way integrated. Be prepared to memorise a dozen username and passwords which will, of course, expire once a month. The systems themselves are byzantine and in no way user-friendly.
Get used to the fact you will not have enough hours in the day to get your allotted tasks and ad-hocs and paperwork done. You will end up either coming in hours before your shift starts or doing it on your day off or both to stay on top of it. An average day would see me starting 90 minutes early and finishing and 60 minutes late, ALL the managers I worked alongside followed this pattern and some came in even earlier. Digest how much all that unpaid time will be if you calculated your true hourly rate.
JL removed a layer of management (Department managers ) meaning the next role open to you is Operations manager. Vacancies for these are like spotting a unicorn, and you will, of course, be competing for them with potentially hundreds of section managers UK wide. Current Operations managers are by and large JL lifers going nowhere, their packages are well in excess of anything comparable in the current market and they know it, so they are all sitting tight until retirement/redundancy.
Sales floor Partners are wrapped in cotton wool, you will find yourself walking on eggshells around them.
Operations managers are by and large sharks, though there is of course variation in management styles, JL seems to have allowed a culture where ruthless individuals work their way to the top ( grievances mean nothing to these people, they have been around long enough to know how to play the game of what they can and can't get away with but stay within the confines of what will not draw senior HR's attention to them) in stores as opposed to the ideals of truly inspiring leaders. Though I truly hope this was just my store and not partnership-wide.