George and Lynne are at a drinks party with Sammy. Sammy asks George if he would like a glass of wine. George refuses asking for a soft drink because he is driving. Lynne also refuses the wine to the dismay of Sammy. George explains she is not drinking because she is the back seat driver.
Sammy is showing the classic signs of alcoholism. He wants to drink but feels he can only justify it if he is drinking with other people. He has bought two glasses of wine but no one wants drink it. There is no way he is going to give it back, or even not drink alcohol so Sammy is stuck with two glasses of wine to drink. After he's had these he will have got a taste and will promptly buy a whole bottle for himself. George should know this and he and Lynne could have at least split that glass of wine to help Sammy.
There are two reasons for Lynne's decision to go tee-total. Firstly she could be pregnant. She's in the very early stages so doesn't want to tell anyone. She's being cautious and has decided not to drink any alcohol during her pregnancy. If we look closely George has parked up wildly and has left his hazard lights on. They never intended to stay longer than one drink and were hoping to go as quickly as possible. This begs the question of why they are there. They are probably making a fleeting appearance at the opening of Sammy's new restaurant. They all (including 'Mantha who hasn't even bothered to show up) think it's a terrible idea to open an all Latvian restaurant. He's wasted his savings and will no doubt drink all his profits.