How much bleed area should I keep for a banner size of 760*1200 mm in Corel Draw or Illustrator any of the two or both?
The cutting of banners is more artesanal than lets say some flyers, you do not have a paper cutter board, but a razor. Sometimes is cutted by hand.
So you need to leave more than the average bleed for printing. I would say 1-1.5cm is ok.
You can ask for the borders to be folded and ironed to the back side. You really do not need more that this 1 cm, becouse, although this folding can be several centimiters width, depending on the banner's size, they can simply leave a blank space of another 4 cm arround.
As far as I'm aware, industry standard for printing at any size is a 3mm bleed or 1/8 on an inch. Although if you are getting it printed professionally, I would ask the person printing it as it may vary.