Although you can update the contact details of a UK domain name on our system:
https://portal.winserve.co.uk/index.php?rp=/knowledgebase/42/How-do-I-edit-the-WHOIS-information-for-a-domain-registered-with-Winserve.html
You cannot change the owner/registrant of a UK domain name through anyone other than Nominet themselves. Nominet are the UK domain name registry and manage all UK domain name registrations.
In order to change the owner/registrant of a UK domain name you have to do it directly with Nominet and they will charge you a small fee to do so. Please see the link below for their instructions on how to do it: