Wires

UPDATE 2-EU seeks to put brave face on Brexit day, warns UK of costs of divergence

Marine Strauss and Jan Strupczewski

divergence@

* Britain formally leaves EU at 2300 GMT on Friday

* EU's strength lies in unity - executive head von der Leyen

* Says EU must focus now on climate change, digital transformation

* Warns UK divergence from EU standards will reduce market access

* Brexit Party lawmakers celebrate UK "independence day" (Recasts with von der Leyen)

BRUSSELS, Jan 31 (Reuters) - European Union leaders sought to put a brave face on Brexit on Friday, saying the remaining 27 countries united can tackle climate change and technological transformation despite losing a member state for the first time.

Britain leaves the EU at midnight - or 2300 UK time - on Friday after nearly half a century of close-knit cooperation, marking a victory for eurosceptics and dealing a major blow to post-World War Two European integration.

"Our experience has taught us that strength does not lie in splendid isolation but in our unique union," the head of the European Union's executive, Ursula von der Leyen, told a news conference ahead of Britain's departure.

"The challenges that Europe faces and the opportunities that it can grasp have not changed because of Brexit," she said, adding that the EU must focus on leading the way globally on tackling climate change, the digital revolution and migration.

After three and a half years of tortuous divorce negotiations, Britain and the EU will now launch new talks on a post-Brexit relationship ranging from security to trade.

The EU told Britain on Friday it cannot expect "the highest quality access to the single market" unless it adopts EU standards on the environment, workers' rights, tax and state aid.

"Without being a member, you cannot retain the benefits of membership," EU leaders including von der Leyen said in an op-ed published by European media.

"Without the free movement of people, there can be no free movement of capital, goods and services."

EU headquarters in Brussels will lower British flags later on Friday. The UK embassy to the EU will similarly lower the bloc's flag, which features a ring of yellow stars - symbolising the member states - against a blue background.

From Saturday Britain will be a foreign country and its officials will have restricted access to EU offices and internal communications. Diplomats of the EU-27 were reminded not to share information with Britain freely anymore.

"THE BEGINNING OF OUR INDEPENDENCE"

In most other respects, however, there will be no immediate change. Britain and the EU enter a transition period until the end of December, giving citizens and businesses time to adapt while the two sides try to hammer out a new relationship.

Trade, fishing rights, security and a raft of other issues are up for discussion.

Although the aim is to achieve a "zero tariff, zero quota" trade deal, the EU says that would also require "zero dumping". It will insist that Britain remain aligned on standards and regulations to guarantee fair competition, but London has said it will not be "a rule taker" and may choose to diverge.

A group of Brexit Party members of the European Parliament left the building in Brussels in high spirits, cheering and waving Union Jack flags as a kilted Scottish bagpiper played.

"Today we celebrate the beginning of our independence," Ann Widdecombe told onlookers before she and the group headed to the railway station to take the Eurostar to London.

Brexit Day will be more muted in Brussels than across the Channel, where its supporters in London's Parliament Square will celebrate their victory following the 2016 referendum in which Britons voted by 52% to 48% to leave the EU. (Additional reporting by Gabriela Baczynska and John Chalmers, Writing by Gabriela Baczynska, Editing by Kevin Liffey and Gareth Jones)