Got to be Pataks, I think its from Leicester, you cannot get more Indian than that! Sharwoods is non Indian fake.
I remember you could only get it in Indian corner shops and I found them to be the most authentic, now we can get them in most major supermarkets in the UK.
I did bring a jar with me on a visit to some friends in America, the customs people took a bit of an interest. I cooked what was probably the first Balti in US history. They should set up a plaque and perhaps a small museum and gift shop.