I think well hear more about Churchill's bust pretty soon. But i think the issue is that it was removed from the Oval Office, not that it was sent back to GB. Back in 2009:
A British Embassy spokesman said: "The bust of Sir Winston Churchill by Sir Jacob Epstein was uniquely lent to a foreign head of state, President George W Bush, from the Government Art Collection in the wake of 9/11 as a signal of the strong transatlantic relationship.
"It was lent for the first term of office of President Bush. When the President was elected for his second and final term, the loan was extended until January 2009.
"The new President has decided not to continue this loan and the bust has now been returned. It is on display at the Ambassador's Residence."
Barack Obama sends bust of Winston Churchill on its way back to Britain - Telegraph
Romney's actual (meaning real) remarks:
"I'm looking forward to the bust of Winston Churchill being in the Oval Office again,"
Romney promises to bring Churchill bust back to White House - Political Hotsheet - CBS News
Maybe by placing it with the diplomat it becomes technically held by the foreign country the said diplomat represents?