The main obstacle associated with showing 3D films at the cinema is cost.  There are two possible 3D options - a new digital projection system or modifying the current 35mm projector.  A new digital projection system and processing equipment would cost in the region of £100,000 along with a new high-gain silver screen (£5,000) and major modifications to the projection room.
The costs associated with modifying the existing system includes a new lens (£1,000) and 3 lens turret (£1,000), an engineer to set up the projector and a new high-gain silver screen (£5,000).  The biggest financial impact is that a licensing fee to Technicolor of 1,500 Euros per film which would make the showing of 3D films financially impossible.