Here in Edinburgh, brown sauce is a very different substance. Although we do still have HP and Daddies', it is not what will get produced when you ask for brown sauce.
Brown sauce, or chippie sauce as it is more commonly know is a thin liquid that comes from a nameless white plastic bottle. The sauce itself is very runny, dark brown in colour and has a sharp, acidic taste and very little in the way of a blend of herbs.
Chippie sauce is by far the most popular topping for chips around here and after getting served in any chip shop you will invariable be asked, "Salt and sauce?". Despite its popular appeal in the chip shop, you can't seem to get it in any supermarket or corner shop. Some chip shops have started selling old lemonade bottles filled with the forbidden sauce on their shelves, but there is no indication as to where this sauce comes from.
In my experience Edinburgh and the areas around it are the only places you can get chippie sauce. Elsewhere in Scotland and England they put a dollop of the thick sauce described above on top of your chips, in my opinion ruining them.