Can cancelling my debit card stop an unwanted auto-renewal?

Long story short, my sister used my debit card to enter a "competition" to buy an iPhone for £1 (clickbait scam). She simply asked me if she could use my card for £1 and I said yes, only after she had done it that she had given my card details to a scam website:/

Reading the T&C of the website I saw that after the £1 was paused a £74 a month subscription would begin. Immediately I've cancelled my card and my statement on my banking app doesn't show a £1 transaction taking place (yet…). All she gave the website was my card number, expiry date and security code (the 3-digit), not my PIN or anything else. She also have them her email but received nothing from them.

Basically all they have is outdated card details for a card that no longer works. Should I be worried of seeing £74 a month drain from my bank account now? Or will they somehow be able to still take my money?

This isn't a direct debit or a standing order BTW, it's simply a third party auto renewal (like Xbox live renewal, and Netflix, etc), so I can't see them having complete access to my bank account from simply knowing digits that can be seen from simply glancing at the debit card. But some reassurance would be appreciated.

No, it can't. You have to deal with people charging your card. If you have tried to cancel it and you can't, because they are a scam etc, then you notify your bank and get them to decline the payment.

Call the bank to stop auto withdrawal. You may still be liable for the charges from the seller.