Best product for removing black spot from Indian Stone

[OMGitsnotgood]

Google tells me that the black spots we have on our Indian stone flagging is a kind of lichen that requires specialist products to remove. These aren't particularly cheap, so thought I'd ask if anyone had any tried and tested recommendations.
Or any that haven't worked successfully that I should avoid.
Thank you

I have done this personally on my own Indian sandstone.

This video shows a really bad infestation of black spots and how they remove it. Basically wash the patio down first, then use Sodium Hypochlorite which is basically bleach but in a much higher concentration than household bleach which is around 5% ish, Sodium Hypo or just referred to as Hypo or soft wash is 15%. Dilution is usually 1 part SH to 5 parts water. In the video he uses a much higher concentration due to how bad it is.

My advice is to test on one paving stone which is exactly what I did before committing to the whole patio area. SH is available on Amazon for £10.49 https://www.amazon.co.uk/LIQUIPAK-Hypochlorite-Cleaner-Swimming-Chlorine/dp/B089B5BKMR

Take a photo of the paving slab. I used a watering can with the solution mixed in at the rate recommended on the SH container and a scrubbing brush to work it in, nothing too intense. Keep checking it and refer back to the photo to see how much it is removing. Rinse down after 20 minutes and check, if it needs another application you will need to go again. Do it on an overcast day, the sun will dry the solution and you need it wet to work. You can use a mist spray on your hose to keep it wet if any area looks like it is drying out.

I watched about 50 videos, researched on the internet because the patio was not cheap and I didn't want to ruin it. I have done it about 4 times over the last decade which is how long the patio has been down. As it is strong bleach please wear old clothes, welly boots, gloves and eye protection.

I used household bleach for our patio, although Im not sure if I had any of this black spot, there are some spots which I didnt get rid of so perhaps that is what it is. Its hard work and my jogging bottoms got ruined becuase of the splashes of bleach. I also worried about the cat walking over the wet ground and splashes of bleach going into soil and pots etc.

Thank you both. Looks like Sodium Hypochlorite is the way to go having watched to video & googled on SH specifically.