This is from the NHS website:
How long to stay at home
If you have symptoms
If you have symptoms of coronavirus, you'll need to stay at home for 7 days.
After 7 days:
if you do not have a high temperature, you do not need to stay at home
if you still have a high temperature, stay at home until your temperature returns to normal
You do not need to stay at home if you just have a cough after 7 days. A cough can last for several weeks after the infection has gone.
If you live with someone who has symptoms
If you live with someone who has symptoms, you'll need to stay at home for 14 days from the day their symptoms started. This is because it can take 14 days for symptoms to appear.
If more than 1 person at home has symptoms, stay at home for 14 days from the day the first person started having symptoms.
If you get symptoms, stay at home for 7 days from when your symptoms start, even if it means you're at home for longer than 14 days.
If you do not get symptoms, you can stop staying at home after 14 days.