I suspect that most Americans will be familiar with both terms, thanks to the prevalence of British television in the United States (thank you, Doctor Who and Downton Abbey).
But, British visitors, you may want to study this list attributed to Quantum Pirate. Asking for a bunglespleen at the grocery store could lead to confusion in the States.
Reader challenge: in the comments, construct a sentence using all of the British terms listed.
-via Dr. Paul Coxon