Graham, you live about 20 miles or less from Renfrewshire where the River Cart flows into the Clyde on the South shore. The Porterfield Castle "Duchall" is lcoated there and you will find several references to Porterfield there. It is in a very delapided state of repair. Good for a Sunday drive for you. To obtain a copy of Frank Porterfields book go on line to the Higginson Book Comapy of Saalem, Massachusetts, USA. You can get a rather inexpensive copy in hard paper there. For a copy of the Crest go to Porterfield jgp on the web adn print out as many as you wish. It is not the best rendering but will give you an idea of the crest. As for the tartan, there is none taht I am aware of: the closest I can come is that we are a sub clan of the Buchanan adn MacNoughton Clans. Hope this helps.