Another great gem with Alec Guiness- and hard to find - is All to Sea (also known as Barnacle Bill). Very funny and quality movie.
All of Alec Guiness movies are wonderful
Some of my favorites are:
The Lavender Hill Mob
The Ladykillers
Situation Hopeless But Not Serious
Kind Hearts and Coronets
The Bridge on the River Kwai
The Scapegoat
Little Lord Fauntleroy