5-lever mortice locks that are not BS3621-approved are usually accompanied with a night-latch as a second lock to ensure security.
If you need to have your 5-lever mortice lock opened, you can call for a locksmith to help you. Costs will be around £90 to £135, excluding any additional charges for emergency, out of hours work. This price will include a replacement lock. If the handles need to be replaced as well, you may expect to pay £25 – £35 extra.