Snakes Alive!

I had quite a scare about a week ago when I found Tali, our little jack russell, staring at a cobra through the animals' 'tunnel' from their room. I was alerted to this when Satchel, our big lab,, went up behind her and dropped down low and started growling. I knew that a fast movement was probably a bad idea but the thing was sitting up and swaying and staring right at Tali and she appeared hypnotised (do they hypnotise? Does anyone know?). I thought it was probably about to strike or spit. so I grabbed her straight up in the air, shoved Satchel with my knees out of the room and ran down the passage with Tali in my arms, shoving Satchel with me! I screamed for Patrick who was down there cleaning. He opened the door, I put the dogs in (Bella our sausage dog was already in there) and we both ran back up. the cobra was still there, Patrick ran for a stick, calling for Fred, the gardener while I grabbed Ziggy, one of our three cats, and literally threw him out of the front door, poor thing!
The two boys ran to the verandah but the snake suddenly disappeared. We all spent the next few hours searching for the snake as we couldn't risk leaving it. We also didn't know if it had come in the house so we had to check right through inside as well. Eventually Fred announced that it was in the storm drain tunnel that runs under our bedroom passage! We blocked it up and tried to smoke it out, etc, to no avail. We temporarily blocked up the drain and then we had to brick up the storm drain the next day permanently. We had discovered that there was a kind of ledge in the drain, under the house and it had obviously gone in there. The ideal snake nest!
This was enough to stress me out (ok, we've had plenty of snakes in the garden, mainly black mambas, as far as we knew, but the boys always got them further down the garden, this one was a but too close to home!)
The end of the story one would think, but no..........
A couple of days ago we noticed that our water was smelling very unpleasant and when the boys checked our well they found a very large dead snake! Charming! (look, I feel sorry for the snakes, we have, after all, encroached on their natural habitats over the years and where are the poor things supposed to go?)
They got the snake out and it was pretty awful, I must say....took us two days to clear the well and tank, even using pool chlorine to sanitise it.
So now we're left with the mystery................
Was it a cobra sitting on the verandah? (apparently mambas also 'sit' up and they're all part of the same family) Was it a cobra in the well? Have the snakes been nesting under our passage in the ledge in the storm drain? Is that why we've had so many snakes compared with everyone else, in our garden? If so, have we solved it by blocking up the drain? Was the snake in the well the one I saw or another one and what was the one in the drain?
Questions, questions....
But mainly relief that for now, at least, we feel a bit safer!
I've posted a couple of photos of the snake in the well and when we got it out.......not very tasteful, sorry about that, but can anyone tell me if it is a cobra?