We know that George and Lynne are at a sporting event due to the crowd members wearing scarves and the well positioned banner at the back of the stand that reads 'SPORT'. What sort of sport it is remains a mystery. It could be football, but it could be rugby. Probability says that it is a football match. George and Lynne must come here a lot to know the people they are sitting next to. This means they are either season ticket holders or it is a low level football match. If we examine this episode more closely, we can be sure it is not a large football match as there seems to be only one person who sells burgers, whereas at a Premier league game there will be numerous burger stands. It could be Tooting and Mitcham FC. They play in black and white but their away kit is red, which corresponds with the scarf the man on the right is wearing.
Does Bob only sell burgers at half time? If they are not available before the game, then this scene must be taking place near the beginning of the second half or in the half time interval. This means that Lynne has been waiting for the right time to address the elephant in the room that is Becky's absence. Unless the fans have changed ends at half time (which is the norm in non-league football) and it is just then that they have bumped into Bill in their usual spot.
George makes a massive assumption that the Bob that Becky has left Bill for is the same Bob who sells the half time burgers. Surely there are a number of Bobs in the area? Maybe George knows something we don't. Maybe Becky has been helping out at the burger stand for a number of weeks now, trying to hide her obvious affection for Bob. This love affair has had a detrimental effect on the quality of Bob's burgers, so much so that only George and Lynne are continuing to buy them. Bill is shocked that George knows that it is Bob from the burger van. Now everyone in close proximity will know that Bill's Becky is with Bob who sells burgers. How embarrassing for Bill. He so embarrassed that by the last panel he has completely moved and is replaced by a man in a blue coat.
In hindsight, Lynne could've continued the alliteration that has been going on, but it's difficult to think that quickly when you're choking on undercooked gristle. I'm sure that as soon as she got home she turned to George and said, "Bugger, I should have said to Bill that Bob's burgers are beastly."