If you've got a stack of luggage and a small dc plus buggy, I don't recommend hanging around bus or train stations but you'd be safe in a Starbucks/Costa Coffee or even a greasy spoon cafe.
But, once again, don't panic as if he's in for the night the chances are he won't be released until mid-morning as there'll be a shift change, plus breakfast for those in custody, and a sorting out of which overnight guests are due to appear in the Magistrates this morning, before he'll be put on the list to be dealt with.
With luck they might charge him and keep him for another night pending an appearance in the Magistrates' on Friday morning, but the chances are he'll be released mid-morning either after having accepted a caution or on police bail pending further investigation.
In any event, you know that the woman you spoke to at the police station will call you if his case is dealt with before 7am and you can, of course, call after that time to find out what the state of play is - and I strongly suggest you do so as it may save you being out in the cold for longer than you have to be.
Keep the possibility of checking into a hotel as a back up plan because your local council has a statutory duty to house you, albeit that this may be in temporary accomodation such as a hotel or b&b. Most council housing offices open to the public c9am, but it's often the case that the Town Hall itself is open 24/7 as it's usually where the out of hours teams can be found.
If you're anxious to leave on or shortly after 7am, I suggest you ask the police to convey you, dc, plus luggage, to the Town Hall and when you arrive tell the porters or other door staff that you are staying put until such time as you are given safe accomodation to go to.
Ideally the police should arrange for you to be collected from your current residence by a dv worker escorted by the police this a.m and taken to a refuge where you'll be given all of the support you need.
However, it's unlikely that you will be allocated a place in a refuge near your current address and you may need to ask your employers for leave of absence if you're unable to commute. As your exbf may decide to turn up at your work being absent for a while will be an advantage.
On balance I would suggest you go for the refuge option as the accomodation is likely to be better than what the council may offer you, you won't be alone with dc in a strange place and, above all, you will be SAFE from harm.
Alternatively, you could ask the police to take you to the home of a family member or, indeed, ask them to collect you, dc, and paraphenalia, and install you in a room at the police station where you won't come into contact with exbf while you wait for dv workers to assist you.