George has just returned home from the 1950s. Even in the 1970s, where George and Lynne live, no one wore a hat to work. Lynne really should have given George a bit of warning as he's been hard at work all day and he may not want to go Line Dancing. In fact he does actually seem a little bit annoyed that Lynne has arranged this without his knowledge.
George's change of mood can only be attributed to Lynne's attire, which is risque to say the least. Whether George's mood will stay as high when he realises that he will go all the way to Line Dancing for Lynne to be turned away for dressing like a trollope and then come home having wasted a whole evening without any dancing, country music or hanky panky (because Lynne's mood change was as drastic as George's, although in the opposite direction due to the aforementioned lack of dancing), remains to be seen.