Unless one of the U.K. food52.com contributors comes online, you might like to check trusted recipes databases for recipe search needs. Foodpickle is better for last minute questions and emergencies when you are cooking and need a quick answer (and I don't know this dish--not common to the U.S.) Here's one:
http://www.bbc.co.uk/food/recipes/traditional_pie_n_mash_76469