1) England does not have an official national dress, unlike Wales and Scotland. Some groups have tried to establish the clothes of Anglo-Saxons or costumes from English traditions as the national dress.
2) The traditional dress associated with Wales is typically a black felt hat, red shawl, white blouse, and full skirt for women. For Scotland, the iconic kilt is most well-known, along with tweed jacket and accessories for men.
3) Ancient Irish dress included the leine shirt, trews trousers, and cloaks. More recently, the costumes of Irish dancers featuring bright colors have become symbolic of Irish national dress.