Existing users, prior to rollout of PayPlans

Hi,

What's the simplest way of dealing with existing users on EasySocial, who joined before PayPlans was installed/rolled out?
Some users have just baseplans, some have business pages so would now be classed as Business Users.

I'd like to give them free membership to base AND business plans for life, if they stick with their existing profile type.

Should I assign them to the new profile types & groups?
How do I deal with Payplans?

Thanks in advance