Mick asks Nessa if she drives and she says she doesn't quoting 'I don't Mick, which is a shame as I loves a good ride', but when Gavin and Stacey are returning from their honeymoon, she is driving a truck and said she used to work for Eddie Stobart.
At the beginning of the series, the scene with Gavin and Bryn at the computer reveals the Shipmans' address to be 17 Lime Tree Avenue. However, when Bryn is typing the address into the Sat-Nav before going to the engagement party in, he types in '21 Lime Tree Avenue'.
When Bryn is talking with Stacey about her getting engaged again the shaving cream on his face keeps changing.
Gwen phones Bryn to tell him Stacey has got engaged (again). The West's live in a row of terraced houses, with no visible alleyway/lane to the rear of the properties, yet Bryn enters Gwen's house via the back door. It wouldn't make sense for him to go around the back (however long that might take) as he only lives a few yards across the street.