If you think about it, each one of those tools has 3 tip, so you've got 15 tips to wreck before you need new ones. 
While I don't know how to do it, have you tried annealing the material to soften it again?
Heat it red and let it cool slowly. If you have a wood stove or fireplace bury it in hot coals and leave it overnight.
No1_sonuk, You are right. I at least have a few more chances if my clumsyness gets the better of me again! And I can make sure that I got a few more in stock too

websterz, I didnt think of doing that. I thought that eventually I will 'cut through' the tempered part but I was wrong! My tool was fuzzed way before I got to that point. And in retrospect, I can only kick myself. You see, I am currently reading through the book "Workshop Technology Part 1" by W.A.J. Chapman, and in the first two chapters, he discusses steel/iron. Effects of heating steel, Reasons for heat treating steel, annealing, Normalising, hardening and tempering etc..... and if I only spared a moment for these two brain cells of mine to work together and think for once, I could've avoided my own frustration!!!

And as you suggest, I could heat up it and bury it in hot coals/sand and let it cool slowly overnight.
I'm guessing that the plasma cutting hardened the edge of the material as well as making a rough-ish edge that resulted in an interrupted cut for the lathe tools. Not an ideal combination for carbide of any type.
Like others have said you could try annealing the metal before you try cutting it. You could also try using HSS tooling on the rough edge before using the carbide.
Some people like using HSS and some like carbide. Both have their place but I use carbide 99% of the time. It's mostly a preference thing. Carbide is hard and hard things chip easily. HSS is not quite as hard and will take more abuse such as with interrupted cuts. There are other considerations to take into account also.
Darren, you are right one the money! I had intermittent cuts on the disc and the edge was hardened way beyond the carbide tool's capacity to cut

So I am going to give the annealing a defenite try!
A also want to start building up a bit more of a versatile tool collection. I am considering these tools mentioned above and also some HSS tools.
Given the machine that you have I would stick with HSS or brazed tip tools, the amount of flex combined with indexable tools didlike of taking fine cuts will make it hard to take small cuts or do fine work.
And as I said on CXhesters, a green grit wheel will sharpen your old bits
Jason
Yes, thank you. I have seen your response on the other forum and replied. I dont like cross-posting. But considering how quiet the other forum can be, I thought of posting here were there is a bigger collective in giving advice. On my particular machine, the 'included' vice on the cross slide is actually becoming a bit of a hassle. It gets in the way if you know what I mean? But If I get rid of the vice, I also loose the current fine feed for the tool post. Anyway, that is for another thread... I am also trying to find a green grit wheel locally, but here in France 'specialized tools' can simply not be found in the DIY shops. Too much hassle for them I suppose. So I have to go and hunt on the internet for something as simple as a green grit wheel and then end up paying extra shipping costs

O yes! And thanks for the link to the diamond tool, I am going to order one!!!

Thanks all for the help/advice so far. I still have a long way to go and learn...