Just wondering about what happens if i have a referral who then starts to build a team and then leaves - do people move up to my team or they then have no sponsor?

No one moves.

ClixSense offers free membership and I see you are a standard member.
As a standard member, you earn on your directly sponsored activities.

As an upgraded member however, you'd earn on referrals upgrades through
8 levels.

ClixSense does not consist of a matrix. There is no forced matrix or roll ups here.

You can see comparison chart:

Best Affiliate Programs | ClixSense

Thanks, yes i am planning to upgrade, just trying to get my head around how everything works right now