You don't have to be separated at all, and he doesn't even have to move to the UK ahead of you if the savings have already been held for 6 months.
ETA: As an example,
You've held the minimum amount of savings for 4 months. He moves to the UK. You have to wait 2 more months to apply as that will mean the savings have been held for 6 months at the time of application.
You already have held the minimum amount of savings for 6 months. You can apply, wait for the visa, and then move the family over in one go.
Are the funds from a sale of a property?