Removed minor siblings from abusive/neglectful situation last night - need to know where I stand legally going forward
(In England for context)
Yesterday I (24yo) was made aware that my 2 sisters (16 and 11) had been left at home alone from Thursday night until my arrival last night. My mother was round at her boyfriend’s house with plans not to return until at least this afternoon.
When I arrived the house was in an appalling state, it’s a borderline hoarder situation with a kitchen that looked ransacked. There was limited edible food in the house apart from pot noodles which they have been mainly surviving on even when our mother is present from the sounds of it.
My mother has a history of being abusive towards me and my siblings (5 of us total including the 2 children) and social services have been involved throughout our lives without much action being taken. The abandonment is a new step up however.
I made the decision to travel to where they live (1 hour away by train) last night when I found out they were alone and only text my mother to let her know once they were in my care, that I was taking them due to her inability to care for them. I let her know I’d be calling social services.
She has since rushed home and is sending messages that are very clearly being crafted with the knowledge that social services might see them. Playing innocent, claiming she was on her way home already before I got there (proven false by my sister having life 360 on her phone showing she only left her boyfriends house 30 mins after we had been on the train back).
I am their older brother but I know this doesn’t grant me automatic legal rights and I am unsure how to move forward. My mother wants them back today as they have school tomorrow and they’re already on thin ice with attendance. Who do I need to speak to to confirm if they will remain with me in the immediate term at least until office hours when I can get social services involved. Is this a case for the emergency line? They are safe and at no further risk of neglect or abuse while in my care so I don’t know if this applies. However if I am compelled to return them to my mother now she has returned I would think the criteria had changed and the emergency line may be needed?
For added context, I have a good job and have the financial means to support them. Certainly more so than their current living situation.
Apologies if this is a bit scattered. Kind of just word vomiting my thoughts right now.
Any advice would be appreciated
EDIT: Thank you for some detailed answers. I thankfully had the foresight to take videos of the state of the house and screenshots of the life 360 at the time. We have lots of evidence.
As suggested I have called the emergency line for their local authority and they agreed the situation wasn’t acceptable and have said that they will notify the social worker who is already involved. I asked that my number was passed on and a note left for them to ring me as a matter of urgency tomorrow.
They did also say that the girls would need to be returned as my mother has legal custody, however a comment mentioned asking the girls as their opinion holds a lot of weight and the older one wants to return (citing school and friends as the reason, the younger wishes to stay which complicates matters)