Right as promised by text earlier and after speaking to legal bod at our place to make sure I am right....
With us (twin valley homes) you can do whats called a deed of assignment..where you assign part of your tenancy rights over to Dave...(hence making it a joint tenancy) but still keep your preserved rights also...the problem is the landlord does not have to accept any assignments and that may well be the case with HH...Best way to check is to read through the tenancy agreement again and see if there is anything about assignments.
If it says they will look at assignments...then the housing act 1988 says that they cannot take away your preserved rights which includes the right to buy
The difference between right to buy & right to acquire is:
right to buy = discounts based on length of time being a tenant (can be quite big discounts too, between £16k & 38k)
right to acquire = can apply only after beig tenant for 5 years and it's fixed discount (between £9k and 16k) regardless of how long been tenant
Hope that helps..if not ...next question???
