I'm an avid fan of the British style (U1-U3, and the whole UK stuff), but maybe because they are not too old school. Back in the eighties, many of these adventures were nearly revolutionary...
Zerakon already gave a short description of The Eye of the Serpent. Inspite of its being a one-on-one adventure you can easily use it with a group. The adventure itself gives the single PC three NPCs to see him through the module.
All that Glitters has a very cool premise: the players get their hands on some scraps of cloth with parts of a treasure map on it. The adventure even gives an explanattion of how the players acquire the cloths (ivory sticks used for the 1e Augury-spell are wrapped into it). The PCs have to deal with cannibals, a magical subway and some curious desert folk, only to discover that the precious, the treasure is but a Decanter of Endless Water.
When Dark Clouds Gather is a bit more cheesy. The PCs stumble across some zealous cleric tortureing a monstrous, winged humanoid. Details are hazy beyond this, but finally our heroes enter a Cloud Giant's cloud castle.
Another fantastic UK module is When a Star Falls (UK4?). It features an unusual set up (Memory Web), an interesting villain, and a very strong story. The PCs have to travel between interesting locations, deal with, e.g., Derro and some machines, avoid a dragon and sort of return to a castle filled with monks.
Ahh, the memories!