When I lived near Newmarket we used a butcher with his own bit in a small supermarket. When that closed he got a job at a local butcher in town. In the former he sold sausages bought direct from a pig farm where they made their own, in the latter they were clearly more mass produced. In both cases they bore the name 'Newmarket sausages' but for the life of me I could not actually tell the difference between those and 'Durham sausages', if they exist. Anyway, the piggery ones were good, the butcher shop ones ordinary. Neither was great in any sense.
In our time, my OH likes sausages, we tried Waitrose and also M&S bio/free range sausages, both highly praised and all the rest of it, but I found them on the bland side because they lacked decent seasoning. I am aware of the fact that many people in the UK do not like seasoning, but take a good look at sausage making recipes and it is hard to find them without. Anyway, whatever the recipe, the actual contents of sausages are never prime cuts, not meant to be, but offal and fat with some red meat and then, everywhere, bread, cereal or whatever is a normal part of them. Vegetarian sausages are nasty dry things without the animal fats. So forget them.
However, since I am neither a sausage lover nor hater, am married to somebody who likes them and have children who would rather live on them than most else, I have eaten them politely for some years. On the English (sausages in Scotland are vile blobs of extra fat and Welsh ones little better) versus French sausages score there is actually little between them other than the herbs and spices used to season them. There are the appalling though to good in both and the ones from local bio producers hereabouts that have far less gristle and fat in them that are fantastic as sausages go.
Having blathered all of that, I eat haggis with relish which is, after all said and done, a sausage. The seasoning in some is great. I also love black pudding! The best I have ever eaten and always tried to get are from Northumberland and there I have never found a French one to challenge those. At the other end of the colour scale, French white puddings knock spots off nearly all bar the mealie puddens in Fife. But then I am no sausage fanatic, so no gloves off to defend my corner.