For clarification, this thread is about the truck companies you usually see when you are out and about.
A thread like this probably already exists, plus i don't really hang around here that much now.
Here is my list. (Doesn't include FarmFoods or Home & Bargains)
Woodside Haulage Ltd.
Kennedy Transport (Usually hauling Guiness)
The uncommon/rare companys.
Nagel Group (Langdons)
Foreign Companies i've seen.
I can also remember seeing a truck from Lithuania, but i don't really remember it.
DFDS (Usually at college)
(Once) Symril Blue Water
(Once) Thomas Boers (NL)
(Once) J.Heebink (NL)
MarkPol, (kinda common, Poland)
Fili Scalabrin (I believe they are a French Company?)
And theres my list, i apologize for it for being long, i do have somewhat of a great memory.