Upvote:5
This page https://www.gov.uk/standard-visitor/if-youre-under-18 implies that you can arrive in the UK without the person named in your visa if you can show that your parent or guardian consents to your travel and accommodation arrangements.
However, in practice youβd need to convince an airline to allow you to board. Airlines are on the hook for anyone they transport who is refused entry on arrival at the destination, so they may very well refuse you boarding unless they could somehow verify the validity of the authorisation, which seems unlikely. So you will in all probability need a new visa.