BRUSSELS (Reuters) - Britain will “continue to play a full role until we leave”, Prime Minister Theresa May told fellow leaders at her first EU summit; but for many Britons in Brussels that is a forlorn hope.

British Prime Minister Theresa May (L) is welcomed by European Commission President Jean-Claude Juncker at the EC headquarters in Brussels, Belgium October 21, 2016. REUTERS/Yves Herman

Formally, yes, the heads of European Union institutions say Britain and its citizens will keep seats at council tables and in Parliament or go on with EU civil service careers in the two to three years left before it quits the 28-nation bloc.

In reality, say British lawmakers and officials in Brussels - some of whom were offered trauma counseling by employers after the Brexit referendum four months ago to the day - they are already being sidelined, and expect further isolation.

“Why should anyone listen to us?” said a British member of the European Parliament who forecast a December mid-term reshuffle of posts such as committee chairs will see many compatriots lose out. “People are polite, sympathetic,” the MEP told Reuters. “But in the end, of course, we are leaving.”

Although May cautioned fellow leaders not to bind Britain by decisions taken without her, as at last month’s summit of 27 in Bratislava, they insist the EU must move on and are annoyed, for example, by London trying to thwart more EU defense cooperation.

The leader of German Chancellor Angela Merkel’s center-right bloc in the European Parliament took to the BBC’s flagship news show during last week’s summit to warn Britons that such awkward tactics risk poisoning May’s efforts to cut the kind of divorce deal she wants, keeping trade ties while curbing immigration.

“That is creating a lot of anger,” Manfred Weber said of British opposition to new plans for EU defense cooperation that London says might hamper NATO. “Please don’t block it because that would have a lot of impact on the Brexit negotiations.”

Acknowledging Britain retains veto powers and votes in the EU for now, Weber said: “It’s a question of behavior, whether you respect each other, not a question of rights.”

“WHY ARE YOU STILL HERE?”

Most British MEPs, including most of May’s Conservatives, opposed Brexit. There has been anger at those who did not; EU chief executive Jean-Claude Juncker demanded of UKIP leader Nigel Farage in the chamber in June: “Why are you still here?”

A German MEP, speaking anonymously since parties have yet to take positions on December’s jobs round, sees a rout of British influence: “The mid-term changes may reflect the new balance of powers, with UK MEPs probably being removed from positions.”

But despite some pressure from fellow MEPs to exclude the British now, lawyers advise that the 73 Britons in the 751-seat chamber must stay - and be able to vote, even on laws that may not affect Britain, or indeed those such as the form of the final divorce that affect it very particularly. Few expect the British to take part in the 2019 EU elections, however.

British officials representing London in the many councils of the European Union in Brussels say they are aware of the delicacy of their position but must defend the national interest on a range of issues - from fishing quotas to budget amendments - that have immediate impacts, before Britain leaves.

Yet as negotiators on both sides are preparing for formal talks to start by March in which continental and British diplomats will find themselves on opposite sides of the table, Britain’s backroom envoys in Brussels are avoiding taking too much of a role in discussions on longer-term policy issues.

That would be “a bit weird”, one acknowledged.

So far, British officials say, attitudes to them in meetings have not changed hugely, as long as they get “the tone right”.

PREPARING FOR THE FUTURE

Britons are keeping especially active in discussions on issues where there will continue to be close cooperation post-Brexit, such as foreign and defense policy - as May herself did during summit talks on Syria, Russia and migration.

May’s predecessor David Cameron even appointed a new British member to Juncker’s European Commission to replace an ally who, like Cameron, resigned after the Brexit vote; Julian King is now running security policy for the EU executive.

British civil servants in Brussels have been assured by Juncker that for now their jobs are safe. But as non-EU citizens they will need special dispensations to work for the Union and many are considering their options.

One EU job not so far open to them, and unlikely to be, is that of Brexit negotiator. Former French foreign minister Michel Barnier, the man Juncker has appointed to run the talks, and his German deputy have not appointed any Britons to their team.

People familiar with the new operation say security will be tight, including to prevent leaks to London, and Barnier has told colleagues he would like negotiations to be held in French - though he denied on Friday being set on the idea.

Britons near retirement are expected to stay on. Of others, some have dual nationality and can switch their official passport. Many in mid-career are looking at the private sector - or at what many expect to be a major expansion in parts of Whitehall, the British government’s administration.

One mid-ranking EU official said he had seen at least one fellow Briton passed over for what, pre-referendum, had seemed a certain promotion: “It’s clear we have no future here,” he said.

“Leaving sooner rather than later may make sense.”