Many times through every episode, the walls wobble, revealing them as set walls.
The room numbers in the hotel frequently changed from episode to episode.
When seen from the inside, the pathway leading from the front door veers to the right. However, outside shots reveal the pathway continues straight on after the door.
The floor plan on the second level changes from episode to episode.
The layout of the hotel from interior shots would place the windowless kitchen hard against the front left of the building, as seem from the outside (if there were space for it at all). In exterior shots there is a large bow window here.
In some episodes, the boom mic becomes visible and the cameraman corrects this by, among other things, zooming in on the scene.
The layout of the hotel does not match the exterior of the building in several spots: there should be bay windows on the kitchen and over the staircase, the bay window closest to the door in the dining room should be flat, and the entire part of the building where the bar is located doesn't exist.
In several episodes, an arch saying "Woburn Country Club" is visible at the entrance to the driveway, revealing the exteriors' location, while the sign from the opening credits saying "Fawlty Towers" (or, in other episodes, "Farty Towels" or other variants) is never seen in any of the exterior shots.
Stoves disappear and re-appear in the kitchen between episodes.
John Cleese says "hand waited on hand and foot" at one point in the episode "Waldorf Salad".