Thanks @babblingbumblingbandofbaboons we'll look into the missing link.
And @Tatatan please email us at contactus @ mumsnet.com and we'll sort out the cancellation for you.

@Tatatan You can cancel your premium account here www.mumsnet.com/settings/premium

I've also raised a ticket internally to get the link changed on the Terms of Use page. @babblingbumblingbandofbaboons Thank you for bringing that to our attention.