The Housing Association should take action, or the council - as this may be considered to be a health risk and an environmental health issue too.
You can avail of the Housing Ombudsman service - which is free to use, quicker than court action and their decision is binding on the Home company (as it is an arbitration scheme).
The Ombudsman will not accept the claim however until you have the Housing Association’s (HA) final response to your complaint.
You therefore need to make a complaint to them now and set out in simple terms which you feel discriminated against and to demand that you want to buy, etc.
The complaints details will be available on the HA's website if you take a look.
Once you have their final response and assuming it does not help, you can then go to the Ombudsman, who will investigate the facts and they will make a decision which if you accept, is binding. You can reach the Ombudsman by email here:***@******.*** or via their website : https://www.housing-ombudsman.org.uk/residents/make-a-complaint/
If the Ombudsman does not uphold your complaint then you can consider court action - you can issue "Judicial Review" proceedings which is where you involve the court, and a senior judge or panel of judges looks at the legality of a housing association's decision. If the judge(s) find in your favour, they will make an order which is binding on the Association (e.g. they may say the decision was invalid or indeed, illegal) and they are then forced to act to sort the problem out. Further, if your human rights were breached then compensation may also be payable.
The issue with judicial review is that the cases are quite complex, but as a result of that, a law firm can usually recover their legal costs from the Association if they win the application. You should be able to have a no win no fee agreement with the law firm, to sue the HA. Or if you are in receipt of means tested benefits then legal aid may well be available to you.
Here are a few firms who specialise in this area :
I hope this helps - please feel free to ask me anything else.