It's only a building, right? The BBC World Service staff who shed an audible tear or two as they said goodbye to Bush House this week were surely expressing no more than the nostalgic attachment to a workplace many of us have felt in our careers. The World Service itself is not closing, is it? It's simply moving down the road, to the new state-of-the-art newsroom inside London's revamped Broadcasting House. There's no need for us to mourn the end of an era, or the passing of something precious. No need at all.

That's certainly what the BBC brass want us to believe. On Thursday, the departing director general, Mark Thompson, declared on the final bulletin broadcast from Bush House that "the BBC's commitment to serve our audiences around the world remains as strong as it's ever been".

And yet those who used to broadcast in that rabbit warren of studios or ate lunch in that Babel of a canteen are worried all the same. It's true that if whingeing were an Olympic sport, BBC employees would take gold every time, but their concern goes far wider than mere self-interest. They are anxious for the future of one of Britain's very few world-class institutions, an organisation that can stake a genuine claim to be an enduring bulwark against tyranny.

Aung San Suu Kyi's regular hymns of praise for the World Service, repeated again when she visited Britain last month, tend to get lost in the comic improbability of her long-held affection for Dave Lee Travis. But her main message is that the World Service got her through 15 years of house arrest, doing for her what it has done for tens of millions living under assorted dictatorships across the globe: providing an independent source of reliable information when all else is propaganda.

Now the World Service will be sharing space with the rest of BBC News, prompting the fear that along with Bush House the BBC will lose the Bush ethos – that distinctive, outward-looking brand of journalism that sought to explain the world to the world. Put simply, the Bush folk fear that they are about to be swallowed up by the domestic-facing BBC. "There are days when our international agenda is completely different from theirs," says one newsroom veteran. "The World Service will be submerged, those micro-climates will no longer flourish."

There is heavyweight support for that concern. Professor Jean Seaton is writing the latest volume of the BBC's official history and recently visited the new, giant newsroom. The kit is terrific, but she was worried by the "hotdesking" arrangements that mean the World Service will no longer have its own, dedicated place. "It looks like a machine for producing a singularity of view," she says.

She can see the efficiency in merging all reporting, but worries that will endanger what makes the World Service unique, namely, a culture that "empathises with news values elsewhere", that strives to understand what matters to Nigerians, Turks or Vietnamese rather than just Britons.

This fear is compounded by the other big change about to hit. From 2014, the World Service's budget will no longer come from a Foreign Office grant, but from the licence fee. Without its own income stream, the full range of output that once emanated from Bush House will have to fight for cash alongside sport, local radio and everything else. Or, as one much admired BBC foreign correspondent puts it: "The Swahili service will have to take its chances alongside Strictly Come Dancing." That, say the Bush folk, is a battle they will always lose. How could BBC bosses justify depriving licence-fee payers – TV viewers in Britain – of a service they use in order to fund one they don't?

I suspect some of those now anxious would be reassured if they had overheard my conversation this week with the BBC's chairman, Lord Patten. He insists he is a genuine friend of the World Service: he was a regular listener when in Hong Kong and Brussels. "It would be absurd to undermine an institution that the rest of the world would give its eyeteeth for," he says. "I'm not going to allow the standards, integrity and quality of the World Service to be undermined."

Patten reckons that the World Service audience of some 180 million gives Britain extra global clout – including in the corridors of Washington – and he doesn't want to throw that asset away. He points too to the presence on the BBC Trust of an international trustee, suggesting that, between them, they'll fight the World Service's corner. As for the fear that a cherished Bush ethos is about to be lost, he declares it "patronising to think there is a separate World Service journalism that is somehow superior to what, say, Jeremy Bowen or Stephanie Flanders are doing".

But that is not quite the point. The issue is not about quality, but about focus: which audience are you addressing? It's the World Service's long-established empathy with its international audience that could get lost, especially since, by 2014, it will have shed a quarter of its staff. And, while Patten's support is reassuring, it can only give temporary comfort. He won't be chairman for ever; the new funding setup will still be in place when he's gone, replaced by someone who might defend the World Service less vigorously.

The only long-term hope is surely to persuade the licence-fee payer that the World Service is worth the money. Devotees like Suu Kyi help, but better still would be if licence-fee payers could see a direct benefit. One neat idea comes from the former Bush presenter Claire Bolderson: why not have the language services broadcast to diaspora communities here in Britain, including some of those who currently feel most alienated?

Put the Bengali, Urdu or Somali services on digital radio, she says, letting, say, British Somalis know about "the latest fighting in Mogadishu but with an update on Lords reform". Such services could, she predicts, strengthen the attachment of those communities not only to the BBC but to Britain itself.

Whether that idea flies or not, the BBC needs to think of something. In the age of soft power, the World Service may well be the institution that does more than any other – including the army – to project British influence in the world. It has a noble past: it's a form of lunacy that it should now be made so anxious for its future.

Twitter: @j_freedland