Other mistake: After the wedding when everyone is outside, Smithy says he has forgotten the maps that gave directions to the reception. Bryan says he can use the sat nav in his Picasso and tells everyone to follow him. But he was driven to the church in the Bentley with Stacey, so his car wouldn't have been there.
Continuity mistake: At the reception, Dawn is talking to Pam and Gwen about the fact that she and Pete's sex-life is dead. Then, Smithy taps on a glass to indicate the speeches beginning, but as the glass is being tapped Smithy is in the shot with his blazer on, talking to Bryn. Then the shot pans over to the other end of the table, and Smithy is suddenly stood up with his blazer off.