Please refer to the deletion link: you need to make a phonecall to delete your account.
URLS:
http://www.williamhill.com/
https://williamhill-lang.custhelp.com/app/answers/detail/a_id/156/kw/cancel%20account
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.