There are so many things wrong in this meme that it makes my head hurt. First let's start with that expression, "directly above my head." The only way for the sun to be directly over your head, or at least apparently so, is at local noon on the correct date at a location somewhere between the Tropic of Cancer and the Tropic of Capricorn. This is not true at the "bottom" of South Africa, and it's very definitely not true in the UK, where the southernmost point, in Cornwall, is nearly 50 degrees north of the equator.
So the crude little drawing of the sun shining down on the UK and another sun shining down on South Africa is just a lie. And then there is the scale of this ridiculous drawing. It does make a difference that the sun is 93 million miles away.
It is, on the other hand, quite possible to see the sun in the sky in both London and Cape Town at the same time. And there is nothing in the globe model that prevents this. They are only, after all, two time zones and 83 degrees latitude apart, so there is nothing in the way of the sun from either location. Why is this such a difficult thing to understand?
You can't, and I have said this many times, debunk a model by misrepresenting it. This is just one extremely blatant example of this kind of tactic.
And then there is the second half of the meme. Which backfires. Why? Because the angles at which a pair of observers would see the sun from London and Cape Town in the flat-Earth model is something someone can easily calculate, given the date and time and a little trig. And it wouldn't match the actual observations for those locations.
Because, and it's getting wearying to even say this, the Earth is not flat.