Wa alaikum salaam
Unfortunately, we can’t help people who wish to buy a house under the Right to Buy scheme.
Under Right to Buy, the housing association is likely to want a legal charge on the property for 5 years. The islamic bank can’t allow this.
But even more importantly, unlike a mortgage, you’re not buying the house yourself and “borrowing” money from a bank to buy it. Instead, woth these home purchase plans you are buying the house in partnership with the Islamic bank. The housing association will not sell to the bank under the Right to Buy scheme. Even if they did allow, you will have to forfeit any discounts.