FWIW all the information in an e-mail header can be manipulated by an unscrupulous person. The club have been very good in being open and honest about this straight away, many organisations would not be as proactive in letting their customers/clients know of the possible breach.
The link in the e-mail loads a javascript file that identifies as ransomware on my virus scanner. If you have clicked on it then I would make sure you have a valid backup of your important data and roll back to prior to clicking the link if you are able.
Find out where else your details might have been leaked here:
https://haveibeenpwned.com