Private covid test

[JS87]

I would be quite happy to pay for a covid test for my child if he became unwell and school insisted on a negative test if it would speed up the process (and help with my husbands mental health).
Ideally I would like to order a swab to have in stock ready to do and send back at the first sign of symptoms
Does anyone know of suitable providers? Many private test websites say they won't test symptomatic cases. I did find one that send test needed to be sent back within 30 days but others don't give a turnaround time for how long you could keep one. I imagine the solution may have an expiry date but I expect it is at least a month.
I just don't know how easy it is going to be to get a test for children now with the new prioritisation list.

Zoomdoc sell a “standby” test which you can have at home waiting and return in the next year or so, whenever you get symptoms.

Vivoclinic will do tests for people who believe that they have the virus, the test is posted to you, you do the swab and send it back, they get results to you within 48 hours.

I haven't done it; I booked a private travel test with them.