For the last few years, the Greek request for the return of the Elgin Marbles has altered from the original claim that disputed the legality of ownership & wanted full ownership rights given to Greece. As a way of getting around the anti-deaccessioning clauses in the Museums Act, in addition to their rejection of any claims of ownership, they have said that they would be willing to accept the Marbles on permanent loan. However the British Museum has still rejected such requests, even though they can not fall back onto their previous reasoning that the Museums Act is what is preventing them.
However, there are many other examples of them giving items to other museums on very long term loans (effectively what Greece is asking for). The article below covers just one of many examples.

From:
Yorkshire Evening Post

11 May 2005
A gift to the gods…and a godsend for museum
Bronze Age sword takes centre stage in £250,000 revamp
BY PAUL JEEVES

A Bronze Age sword, possibly cast away 3,000 years ago as a tribute to the Gods, has been returned to its Yorkshire home.
The ancient blade is the centrepiece of an exciting new exhibition at Scarborough Castle following a £250,000 investment by English Heritage to transform the 12th century fortress into a world class tourist attraction.

Many other artefacts are also being displayed for the first time in the newly-refurbished Master Gunner’s House – itself a unique survivor of the post medieval period. The mass development has also included the launch of new interpretation panels, tea room and an interactive display for less mobile folk.
The blade was originally discovered in 1980 by archaeologist Tony Pacitto, who stumbled across the find on the final day of a dig to investigate a medieval hall at the castle.
Ritual
The subdued glint of bronze in a muddy pit turned a routine shift into the find of a lifetime.
Although no one can be certain, experts believe the blade may have been a ritual offering.
This theory is backed by similar discoveries elsewhere in the country.
Cast as a single piece of metal, it would have been a highly-prized possession.
Ever since it has been kept under lock and key at the British Museum. But now it has finally been returned to its origins.
Nicola Bexon, English Heritage Marketing manager, said: “Getting the sword back on home turf is a fantastic coup and we are confident it will be a massive attraction. We’re grateful to the British Museum for allowing it to return on loan. The relic is a powerful reminder that the headland’s history goes back much further than the present Norman castle suggests. Our aim is to tell this story and make a visit both more fascinating and accessible.
“This investment underlines our commitment to ensuring Scarborough remains a premier tourist destination.”
The Master Gunner’s House probably dates to the late 17th century. Before being converted into the chief gunner’s residence in 1740, it was used to store gunpowder. The castle’s prominent position ensured its batteries were manned well into the 18th century.
However, this did not prevent the American privateer and founder of the US Navy, John Paul Jones, sinking two navy ships in the bay below in 1779.
Around the castle new panels have been erected tracing a 3,000 year timeline. Costumed characters are depicted, each with an artefact displayed in the gunner’s house. These include a soldier with part of a German shell which landed on the town in the 1914 bombardment.
Other relics include a jet cross, Roman pottery vessels and a bearded face which once adorned a 13th century Scarborough-ware jug. Scarborough Museums and Art Gallery has kindly loaned some of the artefacts.
Scarborough Castle is open daily from 10am to 6pm.