I don't mean the flat 4 inch wide slices but the proper sausage with a skin, just over an inch thick.
Where can you get it? Tried all the supermarkets with no luck.
It's luvverly sliced or quartered and then fried as part of breakfast. 
I think true liver sausage (
liverwurst) is the 4 inch wide stuff.
The smaller diameter version with the thicker skin is, I think, the more spreadable pate form, frequently more heavily smoked as well.