The page is called My data. Choose Download my data for a copy, or request deletion from the same page. Go to your account and open My Data. From there you can request a copy of the information held about you, or ask for your account to be deleted.

Getting a copy
Request a download and you will be sent the information held about you. This is your right under UK data protection law and you do not have to give a reason.
Deleting your account
Request deletion and your personal data is removed in line with the privacy policy.

What deletion cannot remove
Some records have to be kept by law. A business is required to keep invoices for years for tax purposes, and that obligation sits above a deletion request. Those records are kept to the minimum necessary rather than deleted on request.
Businesses hold their own records
Each business you have used is responsible for the information it holds about you. Where you want a business to delete what they hold, ask them directly as well.
Before you delete
Download a copy first if you might want your receipts or history. Deletion is not something that can be reversed later.
Common questions
How long does a request take?
Data protection law allows up to a month. Most requests are handled well inside that.
Will deleting my account cancel my bookings?
Deal with any upcoming appointments first, and tell the business, so nobody is left holding a slot for you.
Does deleting stop marketing?
Yes. It is also worth unsubscribing directly, which takes effect immediately.