If you mean the other two are your lodgers then, no, they don't have much protection. If you just mean they don't have a written contract with the landlord but pay him rent then, yes, they do have a contract albeit an oral one with him.
If you wanted to stay there it might be in your interest to ask now for a new 6 month contract with your landlord, this would give you security during the sale of the property and the new landlord would have to take you on with your new AST.
However, as far as the tenancy goes, you dont actually have to do anything unless you want to. Even at the end of October, unless you decided to move out, the tenancy would lapse into a periodic one with the same terms and conditions as your existing (except for notice periods). It's very difficult these days to evict tenants unless theyre at least 2 months behind with rent or breaching other major terms of their contract, even at the end of a fixed term tenancy.