Rubbish.
No experienced geologist would tell you such rubbish. Your "geologist" is a total amateur.
The African plate is NOT being subducted (to any great extent) under the Eurasian plate. End of story.
An easy way to see that your "geologist" is wrong, is to note that if you have two continental plates colliding (like India and Asia) then the trenches and sea-areas between are squeezed out of existence. That is, no more Mediterranean Sea.
The currently accepted theory involves the African plate rotating into (and colliding with) the Eurasian plate which produced a few minor spots of subduction, but thats all.
The currently accepted theory has the African plate being carried east away from the mid-Atlantic ridge by thousands of kilometres and at the same time being carried west away from the Indian ocean ridge by thousands of kilometres (yeah, I know this doesn't make sense), which has produced millions of square kilometres of new sea-floor.
Now, if you produce all of these millions of square kilometres of new sea-floor, then you have to lose millions of square kilometres somewhere else (by subduction), and that certainly is not what is happening between Africa and Eurasia.
And, in any case, you must be really desperate to believe in plate tectonics, if you think that having the African plate being subducted under the Eurasian plate would somehow solve the problem you are trying to solve.
Why don't you try to draw a map of the mantle currents (which are supposedly causing the plates to move) beneath the plates, all of them. If you do try, you are doomed to failure (which is why such a map has never been drawn). You are doomed to failure, simply, because plate tectonics is wrong.
By the way, your statement "As the map below shows, the movement is towards the North-East and North-West; giving a net movement in a northerly direction." doesn't make any sense at all (its just wrong).
The little arrows on your map, are velocities (usually cms/yr). They say that the left side of the African plate is moving (at some non-zero velocity) towards the east (and also towards the north) and that the southern right side of the African plate is moving (at some non-zero velocity) towards the west (and also towards the north). But, this situation exhibits exactly the same problem that you are attempting to explain away.
Anyway, why do you think that the little arrows showing the direction of movement of the African plate, vary by close to 90 degrees? Two arrows on the African plate point NEE while the 3rd points NW. Don't you think that that is very strange? Two very different directions for the same plate.
