At several hotels I worked at we had lean versions of heart-healthy chicken & apple sausages on our breakfast menus. These were always popular and some brands were quite good. One brand in particular was flavored w/ sage and I loved them!
At Alaskan resorts we always served reindeer sausage as well- VERY popular w/ tourists!
The regional differences are mainly the herbs and seasoning put in them. I would say that British recipe sausage would be considered mild, meat/ pork and or beef, breadcrumbs, herbs, onion and different seasonings to give the flavours.