The one comes to my mind is C & A.
Still going strong in Europe, they just pulled out of the UK. When the likes of Asda started selling really cheap clothing, C&A were no longer the budget option, nor the quality option, caught in the middle.
Pretty much the same has happened to Wilko. Undercut by the likes of B&M offering cheap tatt. I wouldn't buy any tools from the likes of B&M, for example, as you know it would last about 6 minutes, whereas Wilko tools were usually of reasonable quality.
I will be sad to see Wilko go. Where will I go now for my paint, light bulbs, seeds, etc? For those living outside the big cities, with the closures of Woolies, Bhs, etc it is becoming increasingly difficult to buy stuff for the home and garden of reasonable quality at reasonable prices. On line, it is very difficult to judge the quality of what you are buying. I suspect that is the reason the likes of Wayfair are taking off, although never having used them, they do come across as more like an online version of B&M than Wilko.