Massive scale fraud and ID theft.

born_again

Action fraud will do nothing. They are only the reporting face of the police. To massage the crime figures.
Maybe raise a complaint with the police, as this really should be a easy case with all the evidence.

https://www.policeconduct.gov.uk/complaints-reviews-and-appeals/make-complaint

Then maybe follow your sisters lead & move away.

elsien

You can  make a formal complaint to the police if you disagree about the actions (or lack of) that they are taking. But they cannot make her pay for your damaged car. That would require court action  - you can formally ask them why she is not being charged with any offence, although ultimately that is the CPS decision not the police. You could ask to speak to the sergeant on shift first before deciding whether to take it further or not. 
If you have evidence you can make a small claims court case against your mother for damage to the vehicle.
If the police have issued a harassment warning to her and she keeps coming back then they can prosecute her.
You can also look at an injunction to keep her away from you - you would need to discuss that with a solicitor to see how much evidence you need.
It is not correct to say that nothing can be done. But it does require you to report and report and report in order to reach the evidence thresholds. 

SusieT

So, complain in writing to the local police, and if possible get your sister to complain or to write a letter backing up your complaint saying that due to them failing to act in 2018, that the behaviour is continuing with you and they have still done nothing. If they do not come back with a satisfactory answer then go to the police complaints. Have a protective cifas (you probably already have) put on your credit file. Get the finance company to work with the police, keep reporting every little thing she does as although it is tiring and you will feel its not worth it, eventually they will have enough individual things and be so fed up with herthey will act.
Keep a bullet point list of date, time, short desctiption of what she did, how much financially it cost.  Small claims court for financial things, and also take out a court order for her to stay away from you.
Use a new email address for the credit reference agencies (make sure she has not set up forwarding to her on your old email address first) so she will not be notified about the change. Change all passwords so that again she cannot gain access to any online accounts that you have - even non financial things like forums. See if you can get face recognition or fingerprint set up as access to bank accounts on smartphone, and see if you can use a card reader for all laptop type online transactions, so that a code is only generated if the actual card is used. 
Good luck with it, what a horrible position to be in

GloriaShaw85

https://forums.moneysavingexpert.com/discussion/comment/79508707#Comment_79508707

Upon ALL’s advice I HAVE reported to the police who said report to AF. REPORTED TO AF WHo STATE

The use of another person’s identity, often referred to as identity theft, is not a police recordable crime.

so what on earth am I meant to do?!? This isn’t getting investigated. I just have to plead to everyone to believe it wasn’t me and write off everything whilst our mother continues this sham and gets away 

GloriaShaw85

SusieT said:

So, complain in writing to the local police, and if possible get your sister to complain or to write a letter backing up your complaint saying that due to them failing to act in 2018, that the behaviour is continuing with you and they have still done nothing. If they do not come back with a satisfactory answer then go to the police complaints. Have a protective cifas (you probably already have) put on your credit file. Get the finance company to work with the police, keep reporting every little thing she does as although it is tiring and you will feel its not worth it, eventually they will have enough individual things and be so fed up with herthey will act.
Keep a bullet point list of date, time, short desctiption of what she did, how much financially it cost.  Small claims court for financial things, and also take out a court order for her to stay away from you.
Use a new email address for the credit reference agencies (make sure she has not set up forwarding to her on your old email address first) so she will not be notified about the change. Change all passwords so that again she cannot gain access to any online accounts that you have - even non financial things like forums. See if you can get face recognition or fingerprint set up as access to bank accounts on smartphone, and see if you can use a card reader for all laptop type online transactions, so that a code is only generated if the actual card is used. 
Good luck with it, what a horrible position to be in

thank you for the advice