I am not from UK and I find this macro obsession quite weird, and somehow damaging.
Don't focus on carb, protein and such, but on food. Beans, lentils, chickpeas in a salad, soup or stew with a lot of vegetables, herbs, spices, are still carb rich and good for body, soul and hair. Beans are very rich in biotin, which is the most important nutrient for hair quality.
Think food more than macronutrient and remember that the countries which are protein heavy are also the heaviest in term of population. Australia meat 3 x a day vs Japan, rice 3x day. The difference is how much they eat.
I don't eat any meats, and I eat for health , so I make sure I have several colours of vegetables every day. You are what you eat. A kiwi is carb, but so rich in mineral and vitamins. Why would anyone consider it the source of weight gain. Carrots, sweet potatoes , are all on the no-no low carb list, but both do wonder for skin and hair as they are very rich in vitamin A. A vitamin A deficiency will cause hairless.
Consider your portions as well. Italian women eat pasta every day, but their plate is way smaller and never loaded with sauce or cheese the way it is served in most countries outside Italy.
If you were to focus on a nutrient, I would say, go for fibre. Everything else will fall into place. There is also emerging science on how gut health impacts hair.
It is easier to blame a macro than oneself. You just ate too much of the wrong food. Now you need to eat less, and eat the right food. It will take time but that's fine.