Hello, thank you for the question.
I am a UK qualified solicitor and happy to help.
In relation to the disclosure of personal information, I would contact the Information Commissioner' Office on 0303(###) ###-####to see if they agree the housing association have breached your rights under the General Data Protection Regulations (GDPR). If so, you can sue the housing association for compensation and they would also be fined by the commissioner's office for the breach too.
Regarding the harassment by the tenant, you should report this to the Police on the 101 number as by the sounds of it, this sounds like serious harassment to include the stalking and abuse. Check if the Police can help. If they say this is a civil matter, you need to apply to Central London County Court for an injunction.
You will need to complete the attached form N16A and send to your county court with a fee of £150 payable to HMCTS (unless you are in receipt of benefits in which case you can get a fee exemption so you do not have to pay). You can pay either by cheque or attend the court and pay at the counter.
The court will list a hearing where you attend and ask the District Judge for an order and the injunction against the tenant. The application would be made under the Protection from Harassment Act 1997.
If granted, the Order is then served on the individual concerned and they are bound by the court order - if they breach the order, they are in contempt of court and could well face a fine and a prison term.
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