That should never happen. However, although the bank sold you the mortgage, you are complaining about the endowment which was sold through Standard Life - even if the adviser was employed by the bank, they were probably acting as an agent of Standard Lifeand therefore, the responsibility for the advice provided lies with Standard. It is not always quite that straightforward, but usually that is the case.
In any case, the FSA would not be happy as their big focus at the moment is on ensuring companys treat customers fairly and one of the key customer outcomes is that consumers do not face unreasonable post sale barriers imposed by firms to change product, switch provider, submit a claim or make a complaint.
If your bank were to withdraw any facilities, I would take them to FOS.