Message keeps showing to users who have closed it and already subscribed

So I've checked the options as follows in Global Settings:
- Show message after: 5%
- Hide Message after: 59 seconds
- Closing the message: Hide all messages for the visitor (with both subsequent dropdowns blank)

I've then created a form for mailchimp subscriptions which doesn't override any global setting and works fine...EXCEPT:
1. When a user/visitor subscribes, the slide in stays there. I wan't it to close and stay gone for them. I know this is down to session or possibly IP depending, so I know it's not bullet proof. However, currently it seems like it doesn't even attempt to do this.
2. When they click Close it comes back on other pages and return visits.
3. Subscribed users see it on subsequent pages and return visits.

Thank you for your help...and all the awesome plugins :slight_smile: