leave Job
from my experience, when a member of staff leaves, we usually inform bupa etc right away. Bupa usually look for details etc of the member and leaving date so that they can contact him/her directly to establish if they wish to continue. After all from Bupa's point of view they are losing a client.
But to be on the safe side I would find out who is the group advisor for your company and give them a ring.
Also, you would have been getting a discount as a group but this discount is also available to you if you are a member of a credit union. So make sure you get 10% discount if you are in a CU.
Cheers.