Not sure if this might be of help. I have had an email this morning from the Early Years Alliance. The guidance has changed in terms of who to contact if you have a COVID case confirmed in your setting. (The bold and red font is my emphasis) I just wonder if they may be able to offer advice for your situation? Maybe worth a phone call. The email says:
However, this guidance has now been updated to state that: "You should contact the DfE Helpline on 0800 046 8687 and select option 1 for advice on the action to take in response to a positive case. You will be put through to a team of advisors who will inform you what action is needed based on the latest public health advice. If, following triage, further expert advice is required the adviser will escalate your call to the local health protection team."