For some reason, people like to wax poetic about old TSR modules like Keep on the Borderlands (What if nearly-identical monsters lived in nearly identical caves?!?) and the Giants series (What if you fought the same kind of giant 15 times then got to another one and fought a different kind of giant 15 times?) despite the fact they all bite.
With the bar for appreciating TSR modules so low, I am kind of amazed I've never heard anything about the TSR UK series which--you guessed it--featured artists and the writers from the UK, including, I think, early White Dwarf adventures. They're a mixed bag but as a whole feature off-beat art, excellent maps and some intriguing structures (in The Gauntlet, for example, you have to take over a dungeon, then hold it against an assault).
Do you remember anything about UK1-UK7? Don't be shy in the comments.