How do you say bathroom in Great Britain?

Answer 1

The origin of the (chiefly British) term loo is unknown. According to the OED, the etymology is obscure, but it might derive from the word Waterloo. The first recorded entry is in fact from James Joyce's Ulysses (1922): "O yes, mon loup. How much cost? Waterloo. Watercloset".
Other theories are:

• That it derives from the term "gardyloo" (a corruption of the French phrase gardez l'eau (or maybe: Garde de l'eau!) loosely translated as "watch out for the water!") which was used in medieval times when chamber pots were emptied from a window onto the street. However the first recorded usage of "loo" comes long after this term became obsolete.
• That the word comes from nautical terminology, loo being an old-fashioned word for lee. The standard nautical pronunciation (in British English) of leeward is looward. Early ships were not fitted with toilets but the crew would urinate over the side of the vessel. However it was important to use the leeward side. Using the windward side would result in the urine blown back on board: hence the phrases 'pissing into the wind' and 'spitting into the wind'. Even now most yachtsmen refer to the loo rather than the heads.
• That the word derives from the 17th century preacher Louis Bourdaloue. Bordaloue's sermons at the Saint Paul-Saint Louis Church in Paris lasted at least three hours and myth has it that wealthier ladies took along "travelling" chamber pots that could be hidden under their dresses whenever the need arose to avoid the need to leave. Due to the popularity of the myth the bowls became known as Bordaloues after the preacher and the name became corrupted to portaloos and sometimes just plain loos due to the habit of shortening words in slang.
• Let us not forget the enemies of England. Armies have a colorful way of immortalising their vanquished foes. When Napoleon's army was finally defeated at "WATERLOO" soldiers would commemorate the victory by doing their business in the waterLOO.
  

Answer 2

Depends on accent, when American film/tv actors try british accents it is said like 'baarthroom' or sometimes 'baath-room'. In truth it is anywhere from barrthrumm through to baathroom. Although the UK equivalents of the American bathroom is loo, lavvy, toilet, crapper or bog.

Answer 3

you say "i have to go to the loo"