"They are from a different country and culture"
"DH has said his mum will 'want to run our household'"
FUCK. RIGHT. OFF. She can 'want' all she wants, buts it is YOUR household and she is a feckin' guest. And I don't give a rat's arse if your DH is fine with mummy taking over, IT'S NOT HER PLACE. If he wanted a wife who would cowtow to his mother, he should have married one from his country and culture. He didn't, so he gets what your culture expects.
I'd hazard a guess that if your DH wasn't coming out with this crap, you wouldn't feel the need to think up rules for MIL/PIL, because you'd trust him to have your back and tell his parents how he expected them to behave. Because some of your 'rules' I'd just class as common courtesy.
"1) I don't want them to take DS out of flat without me."
You're worried about their age, lack of familiarity with the area, traffic, etc., and their lack of English should they need assistance. All fine.
"2) As they will use our en-suite for showers (other bathroom only has low-level shower) I want them to set a time for this rather than tramp in and out of our bedroom when DS is napping/BF/I'm trying to have a break. I need some privacy!"
This is one I see as common courtesy. It's your bedroom, a private space. Of course there should be consideration given to your needs here.
"3) I plan to invite them to some baby classes but not all. I feel it's inappropriate for them to observe baby yoga or swimming as other mums may feel awkward!"
Again, common courtesy. There was a recent thread, might have been Gransnet rather than Mumsnet, where a MIL was all upset about her DIL not wanting them to tag along to similar classes. The consensus was to (kindly) get a grip. And for that very reason, that the rest of the class would not neccesarily feel comfortable, and that it could prevent the DIL from being able to effectively network with the other mums, an important part of these classes let's face it.
"4) Some days I want to take DS out for day without PILs."
Absolutely fine. 'Mum wants to spend time with her baby' shock-horror
.
"5) I want to do all bedtime routines, he's hard to settle so I don't want them coming into our bedroom after 8pm."
There could be some flexibility on this one. You could do it together. Alternatively, point out to DH that if DS becomes unsettled, he can spend the several weeks after their visit re-establishing DS's routine. It can be useful to have a less-than-rigid routine - makes it easier for DC to settle when away on holiday, visiting etc.
"6) I don't want them to bath him without me (I have anxiety re him being left unattended for few secs)."
You're not saying they can't bath him, you're just saying you'll also be there. Absolutely fine.
"7) DH wants to do a mini-break but I can't face a long drive with PILs as I will have to sit in back with no space and I get carsick in the back."
I think you've already taken on board the suggestion of a large hire car where you'll be in the front? I get carsick in the back too, my sympathies. The only problem people with knee problems prefer the front is to allow them to push the seat right back and allow their legs to be fairly straight. WHat she needs is legroom, not the front seat. If you can hire a car with lots of legroom in the back, she'll be fine. Alternatively, can you drive and DH goes in the back?
"8) I hate family breakfasts. I want to be able to grab some toast/coffee after the 7am feed then get showered and dressed before facing anyone. DH thinks this is rude."
Family breakfasts. Sorry, but that sounds grim to me. Our household, everyone breakfasts separately. I'd compromise on this one though, maybe grab some toast, head to the shower and return to sit with a cup of tea after I'd got ready.
I would be having stern words with DH that I do not expect his parents to make my life a misery while they are here, and that you expect him to back you up over his mother's wishes should there be a conflict. Otherwise I'd be going off on a mini-break alone and he could take care of his parents all by himself. Five weeks is a very big ask.