To be paying £50 a month they'd have 2500 contacts on the Standard package or 5000 contacts on the Essentials package, which surely would be beyond a small club.
As far as GDPR goes, I don't think anyone would be able to resubscribe you except you, regardless of how you where unsubscribed and whether it was by accident or on purpose.
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.
