Becoming chicken parents!

My partner and I are going to collect 4 rescue/ex caged hens from a charity here in England this weekend! I’m so excited!
I’ve never had chickens before and I’m looking for advice and guidance, so please help a newbie out; what are some things you wish you knew before first getting chickens? What should we expect with rescue hens? (They will be around 17 months old)
One thing I’m feeling very worried about is predators here in the UK (mostly foxes). We have used galvanised 16g wire and we’ve put locks with bolts on the coop, I just know I’ll be heartbroken if anyone is unsafe or the worst happens, so any tips here would be appreciated!
Thanks! 🐔🐣🌾🐓