Can I go to UK holding an accompanied visa, unaccompanied

You may be refused entry if you have an accompanied child endorsement on your visa and you arrive at the UK border without the person on the vignette, even if the person you arrive with is a parent or legal guardian.

The guidance for Home Office staff states, in part:

Accompanied children at the border
If the child is not travelling with the adult identified on their visa, they may be refused.

The visitor rules state, in part:

V 4.11 Adequate arrangements must have been made for their travel to, reception and care in the UK.

V 4.12 If the applicant is not applying or travelling with a parent or guardian based in their home country or country of ordinary residence who is responsible for their care; that parent or guardian must confirm that they consent to the arrangements for the child’s travel to, and reception and care in the UK. Where requested, this consent must be given in writing.

V 4.13 A child who holds a visit visa must either:
(a) hold a valid visit visa that states they are accompanied and will be travelling with an adult identified on that visit visa; or
(b) hold a visit visa which states they are unaccompanied; if neither applies, the child may be refused entry unless they meet the requirements of V 4.12.

As an English speaker, this seems to indicate to me that an immigration officer could use his discretion to allow landing or temporary admission, but you should not rely on that. It is most likely that you would be refused entry at the border in this case (if you somehow convinced the airline to board you, which is also unlikely).

To avoid any problems, you should apply for a new UK visa. An accompanied child visa can be issued allowing either of two adults to accompany you. (In the case of two adults, only their passport numbers appear on the visa, and they must present one of those specific passports at the border even if they have expired.) You might also obtain an unaccompanied child visa, and in this case you may travel with anyone, or alone.

A child with an ‘unaccompanied child visitor’ visa may travel with or without an accompanying adult. For example, they may have obtained a multi-entry visa and be unable to advise in advance who they will travel with on subsequent trips to the UK.

It clearly states even if the child who has a valid accompanied visa is travelling without the adult mentioned in his accompanied visa can still be admitted to the UK if he is travelling with a parent in this case his father. Please see paragraph V 4.12 and V 4.13 and I quote:

V 4.13 A child who holds a visit visa must either:

(a) hold a valid visit visa that states they are accompanied and will be travelling with an adult identified on that visit visa; or

(b) hold a visit visa which states they are unaccompanied;

If neither applies, the child may be refused entry unless they meet the requirements of

V 4.12 If the applicant is not applying or travelling with a parent or guardian based in their home country or country of ordinary residence who is responsible for their care; that parent or guardian must confirm that they consent to the arrangements for the child’s travel to, and reception and care in the UK. Where requested, this consent must be given in writing.