Household isolation question

[marplemead]

Does anyone know whether the whole household needs to begin another 10-day isolation? We are expecting a call from T&T tomorrow, so can't ask until then.

Day 0 - Person A (adult) takes PCR test as close contact (already been isolating for 5 days)
Day 1 - Person A receives positive result and told to isolate for 10 days along with household
Day 5 - Person B (adult) and Person C (child) receive negative PCR test results but continue to isolate
Day 10 - Person B tests again.
Day 11 - Isolation ends. Person B receives negative result. Person C takes another PCR.
Day 12 - Person C (child) tests positive.

As Person C tested positive after the isolation period ended it isn't clear whether Person A needs to start isolating again if they've already had it. It makes sense for Person B to do so, as they haven't caught it yet.

As its after the ten day isolation period i would think you might have to all self isolate again, has person c been in contact with others, since?

Thank you. Person C has had no contact outside the household.
I've just got off the phone to T&T. They couldn't answer the question and told me to Google it