This is a direct lift from the appropriate legislation including instrument number and revoked legislation, it is actually quite clear:
(c) HM Government
The Cremation (England and Wales) Regulations 2008 SI No. 2841
Came into force – 1st January 2009
Disposal of ashes
30.—(1) Subject to paragraph (2), after a cremation the cremation authority must give the ashes to the applicant or a person nominated for that purpose by the applicant.
(2) If the applicant does not want to be given the ashes and has not nominated any person for that purpose, the cremation authority must retain the ashes.
(3) Subject to any special arrangement for the burial or preservation of ashes, any ashes retained by a cremation authority must be decently interred in a burial ground or in part of a crematorium reserved for the burial of ashes, or scattered there.
(4) In relation to ashes left temporarily in the care of a cremation authority, the authority may not inter or scatter the ashes unless 14 days notice of their intention to do so has been given to the applicant.