* EU leaders meet late on Thursday in Estonia
* Informal gathering follows fizz of initiatives
* Macron speech on Tuesday admired but many wary
* Britain's May to attend, after keynote Brexit speech
TALLINN, Sept 28 (Reuters) - French President Emmanuel Macron can expound his ambitious new vision for the European Union when he meets his fellow EU leaders over dinner in Estonia on Thursday, but is likely to receive only a cautious hearing.
The informal get-together in Tallinn, arranged on the fly before a "digital summit" on issues ranging from data and cybersecurity to taxing online businesses, has no set agenda and could range widely, even allowing for Prime Minister Theresa May to pitch her ideas on Britain's looming exit from the EU.
But four days after a German election that has raised the prospect of months of tough coalition talks for Chancellor Angela Merkel, the most influential EU leader, and two days after Macron's rallying cry for deeper integration of national economies, the focus will rather be on the fizz of new initiatives, diplomats say.
"Macron has stolen the show," one senior EU official said of the dinner debate and which all of the 28 national leaders bar Spanish Prime Minister Mariano Rajoy are expected to attend.
Many admire the youthful new French president's energy and oratory after years in which Paris, long a driving force of the EU, has appeared bereft of self-confidence.
However, Macron is likely to face polite but firm resistance at the dinner to his calls for a substantial pooling of national budgets and a possible breakaway by the wealthy, western states into a deeper monetary union.
Eastern European leaders may caution about the risk of new cleavages on the continent leaving them behind, while there are plenty, like Dutch Prime Minister Mark Rutte, a moving spirit behind the Tallinn dinner, who will sound sceptical about more financial burden-sharing before southern neighbours -- including France -- put their own national budgets on a sounder footing.
Merkel will arrive in Tallinn having lost her veteran finance minister, austerity hawk Wolfgang Schaeuble, who is now set to preside over a German parliament packed with far-right radicals.
Though she welcomed Macron's Europe speech in Paris -- and had discussed it with him beforehand -- Merkel will be unable to commit Berlin to much as she has barely started the process of building what is likely to be a three-way coalition government.
FIZZ OF IDEAS
Brussels diplomats have been left a shade nervous about the leaders being left, unscripted, to their own devices at a time when not only Macron but EU chief executive Jean-Claude Juncker and others have been delivering a stream of ideas. These focus on how the bloc, emerging from a slump and a series of crises, can reinforce itself in the wake of Britain's departure in 2019.
Summit chair Donald Tusk will moderate the discussion and officials say his aim will be try to streamline the debate and get leaders to focus on concrete objectives and policies, to avoid a proliferation of "road maps" and divisive proposals.
The presence of Theresa May, despite Britain's increasing isolation as it prepares to quit the bloc in 18 months, adds an element of embarrassment which may limit talk on new EU plans.
May will arrive with a better sense of whether her keynote major Brexit speech last Friday has succeeded in unblocking talks in Brussels on Britain's divorce package. Negotiators are due to wind up a new round of discussions on Thursday.
EU officials say she should not expect direct feedback in Tallinn from the other leaders, who are keen to let their negotiator, Michel Barnier, handle the process. But she is likely to talk to some of them individually as she pursues her quest for agreement to open talks on close ties with the bloc after Britain leaves.
The EU insists that cannot happen until "significant progress" is made on divorce terms -- notably how much Britain owes. Her speech in Florence has, so far, averted a stalemate, EU negotiators say, opening the way for some positive movement. (Reporting and writing by Alastair Macdonald; Editing by Gareth Jones)