Everything she can do to prep the night before she does BEFORE she’s allowed to do anything “fun”.
Multiple alarms of the loudest most startling kind on whatever she uses as an alarm clock (which is what?) I’d be tempted to get her old style double bell and/or radio alarm and it is placed so she has to physically get out of bed to turn it off.
Then...let her get on with it! Let her be late a few times and suffer the consequences. She’ll soon realise it’s not worth the hassle!
“Problem is we generally take it in turns to work evenings and it's hard to keep a routine going because of miscommunication” sorry but that’s a poor excuse, she needs lunch EVERY SCHOOL DAY, she needs uniform EVERY SCHOOL DAY, she needs her bag ready EVERY SCHOOL DAY
You could have a wall planner up in the kitchen and mark on it PE days and similar - each person has their own colour.
Also how old are your younger ones? Because if they’re junior school age+ they should be starting to do stuff to enable their independence too.
It’s best done as a gradual thing - not left until they’re “old enough” to “be independent”
I raised dd pretty much alone since she was 2, she’s been doing stuff for herself since then. Initially small “chores” like putting toys away, putting dirty laundry in hamper but as she aged up her responsibilities increased.
She turns 19 next month (well in a couple weeks actually) and is now in her own flat, works full time (shifts).
She’s been astounded since about the age of 12/13 at how little her peers do and how completely molly coddled some of them are - at this age (18/19) there’s even a few who STILL aren’t “allowed” to use a kettle or frying pan in case they hurt themselves! Ridiculous!
She’s more than old enough to get herself up and ready op.
“Dd isn't keen on sandwiches and takes a Thermos flask” sandwiches aren’t the only cold lunch she could take. Does she like wraps/pita/bagels, pasta/cous cous/rice/noodle salad, falafel, crackers/crispbeads/rice cakes with cheese/pate/spreads, quiche, pork pies, sausage rolls, Scotch eggs, mini cocktail sausages, savoury tarts...
LOADS of cold things she could have for packed lunch that aren’t “sandwiches”
Lost key - get her one of those coiled cord key rings then attach it to the zip on the pocket inside her bag or the metal attachments on the handles so she can use the key WITHOUT detaching it from the bag. That’s what I did with my dd with similar problem (the key was actually usually in her bag she just had trouble finding it amongst all the debris!)
Although a key safe is a good option too. I’m fascinated by these new “digital” doors (I dread to think what they cost!) where you can lock and unlock your house using your phone! The costs will come down I’m sure and they’ll become a normality but at the moment it still very much feels a “tomorrows world” thing (geez how old does THAT make me sound!! 😂)