Grafton books is a division of Collins, Glasgow. F. Marian MacNeill was a historian by profession. Really good traditional stuff and well laid out. McNeill's book gives several recipies for haggis. It takes about a day to make a haggis from scratch, but very very few people do this as it is particulaly gruesome.
Most people buy their haggis from the butcher's.
See next section for details of how to get some.