If you are the only person in the household with symptoms, we would advise you try to isolate within your home, away from your household members if at all possible. We do not therefore recommend someone comes with you to your test. It is particularly important for you to stay away from anyone who is at risk or extremely vulnerable. More advice can be found here. Ordering a home testing kit may be an option for you.
If multiple members of the family have symptoms of COVID-19, you can travel together but you must each have booked a test.
If you are a single parent, your child (or children) can attend with you.