I had something a bit like this. My scalp became very itchy and flaky. I couldn't see what the issue was so went to my mum's to get her to check it. I basically had big bits of dry skin just flaking off, by big I don't mean penny size but they were flaking in big enough pieces that you could see them in my hands.
I bought a scalp scrub from Le Labo which helped, try and get a sample first though as it is about £30. You cannot use it continuously as it will dry your scalp out, I use it once or twice a month. I also found that some shampoos were drying my hands out really badly so could only think what they were doing to my scalp. I love a range you can get in Poundland. I cannot remember the name but they are small rectangular bottles and all fruit scented. They contain none of the nasties (so SLS free) and they have worked a treat on my hair. I have the banana set, the hemp shampoo, the strawberry conditioner, the ginger shampoo and the tea tree shampoo. For a quid, they're bloody amazing!
I agree, the superdrug range is great. They have a scalp tonic too which is fantastic! I saw improvements after the first use.
I saw this in Superdrug yesterday and it looked very good, I was going to google reviews but having seen, this, I will pick it up when I am next in store