Advice about staying in South Africa

I am a UK Citizen with a South African partner and we have a house in Cape Town.

I visit on a Tourist Visa as I have a business in London and children and need to return every three months to work and see my children.

With the recent Corona disruption I applied and was awarded a 90 day extension to my tourist visa which expired on 13th November.

We had a holiday booked to Mauritius for 14 days which we left for on 12th November and arrived back yesterday.

I had previously planned and booked a return to the UK on 14th December for Christmas.

Upon arrival at Johannesburg the Immigration Officer at passport control accused me of border hopping and said that he was not going to issue a new Tourist Visa and instead was going to allow me 7 days to leave the country and issue a Transit Visa?

I explained that I had a flight booked to return back to the UK on 14th December and that I was not "border hopping" but he insisted this was the case and issued the 7 days Transit Visa.

Now with the latest Covid outbreak and associated travel bans being placed on anyone flying from South Africa it is almost impossible to arrange flights to leave the country.

All British Airways flights to the UK have been cancelled together with KLM, Air France, Emirates, Qatar Airways etc etc.

I did actually manage to book a flight to return to Mauritius last night with British Airways but this has now been cancelled?

Can anyone advise please whether there is anything I can do to dispute the Transit Visa that has been issued?

What is the situation if there are NO available flights to leave South Africa?

I have heard very bad things about the implications of overstaying any type of Visa in South Africa and the bans that can be and are imposed for doing this with little or no right to contest.

I am hoping that someone has found themselves in this situation previously perhaps during the last lockdown and can provide advice.

Many thanks

Adam