We have been having this discussion with regards to the MEL in easyJet. The MEL refers basically to what is technically OK to dispatch with and is thus the\province of the CAA/JAA. The flight deck door locked policy is from The DTI, and is thus different.
Technically, we can have the flight deck door open as we used to, but we would be breaking the law with regard to DTI regulations. Two sets of regulations covering the same subject.