From The Independent, Simon Calder:
I suggest you consider a stop in Egypt on your way back. From Johannesburg, an Ethiopian Airlines flight to Cairo via Addis Ababa costs about £300. For admission to Egypt, the Foreign Office says NHS proof of vaccination is acceptable in lieu of a test. It adds: “Passengers arriving from countries where Covid-19 variants of concern have been identified may be required to undertake a rapid Covid-19 test on arrival, which if positive will lead to a subsequent PCR test to determine if isolation at a government hospital is necessary.
Once in Egypt, assuming you are negative, you could visit the Pyramids, the antiquities of the Nile or the Red Sea tourist resorts around Hurghada or Sharm El Sheikh – which have inexpensive budget flights to the UK. On 21 December, for example, easyJet has a flight from Hurghada to Gatwick for just £43.
You must spend 10 full days away from red list countries to avoid hotel quarantine. After that, you must follow normal rules for travel to the UK – with a pre-departure test, a post-arrival PCR and a completed passenger locator form.
Overall, the total cost of an Egyptian diversion will be far lower than the price of hotel quarantine, and you should have a much better experience – though I cannot guarantee that Egypt will avoid being next for red listing.
my emphasis