If you are asked to self-isolate you need to:
You should make sure any items delivered are left outside your door, as appropriate for your home.
If you live with other people, you may have to take extra measures to reduce the chances of onward infection, such as staying in a separate room and regularly cleaning shared kitchens and bathrooms.
Updated 16th March 2020: Anyone living alone who has a new continuous cough or a high temperature (above 37.8) should self-isolate for 7 days. If you live with more than one person, and any of you displays these symptoms, then your whole household should self-isolate for 14 days.