Following yesterday's interesting debate in the comments here's some background reading on mealtime variations:

• History Magazine: What time is dinner?
  "The modern confusion arose from changing social customs and classes, political and economic developments, and even from technological innovations" - useful summary of what's changed and why.
• English mealtimes explained
  Summary for foreign businesspeople which illustrates some of the issues but clouds them rather than making them any clearer.
• Wikipedia: Tea
  Fascinating explanation of teatime variations. Meat tea anyone? See also Carry On favourite Tiffin.
• Teas and Other Afternoon Parties
  1922 etiquette guide from Emily Post. Starts out fluffy, ends up serious.
• The motley cuisine of the United Kingdom
  "Greasy and unhealthy food is very easily obtained". Yeah, baby. We're no. 1!