Social services know everything about my brother including the stealing from mum and tid write it head ohe class a drug use in her house and they still choose to not get involved.
I'd ask CAB if any of the following ideas would be an advantage or detrimental to your situation:
Email the head of social services and make a formal complaint ,and your MP. Years ago I worked for a govt dept and MP enquiries had people 'jumping through hoops'.
If your mum has no capacity then I can't see you would need to tell her you are are applying for deputyship , she's not going to understand is she? I think you can use your mum's money to pay ,although I can see that is difficult if you can't access her account!
Another thing ,could social services be telling you to apply for deputyship as it is in her best interest for that to be under way before they act?? Systems are so complex.
Some of your comments suggest mum does have capacity. Eg permission for pin change and her conversation with OT. Is this why s.s and Police can't act?
Hope CAB can help