The 300,000-strong community in London alone makes it by some estimates France's sixth biggest city, giving it the nickname Paris-on-Thames.
In Europe's financial hub, the socialist presidential candidate initially tried to play down concerns over his intention to crack down on the financial world if he ousts President Nicolas Sarkozy in May, telling one journalist: "I am not dangerous."
But in a speech to students at King's College London, Hollande insisted: "We need a market that is better regulated. Of course we need banks and financial products to keep the economy running, but we don't need banks that speculate.
"We need to bring in rules against excess," he went on.
"What caused this four-year crisis if it wasn't financial products that were not sufficiently controlled in the United States?
"What caused the crisis in the eurozone if it wasn't uncontrolled speculation?"
Hollande's manifesto pledges to renegotiate an EU fiscal treaty, and his description of the financial world as his "adversary" at a recent campaign rally, have ruffled feathers in the City of London financial district.
The Frenchman repeated his commitment to renegotiating the treaty in London, while urging Britain to take a more active role in the EU.
"We need a Britain that takes a full part in the European adventure," he said, after clashes in recent months between British premier David Cameron and Sarkozy over how to end the eurozone debt crisis.
Hollande, given by opinion polls as the likely winner in the two-round presidential election in April and May, added that he would seek stronger defence cooperation with Britain if he won.
The frontrunner played down the lack of a meeting with Cameron in London, who this month wished fellow conservative Sarkozy luck in the campaign, describing him as a "friend".
Hollande held talks with Ed Miliband, leader of Britain's opposition centre-left Labour party, and said he had not asked for a meeting with Cameron.
"Today I felt that my priority was meeting my friends from the Labour Party," he said.
"The day might come, and it might be soon, if I manage to convince the French voters on May 6th, when I will have to meet Mr Cameron."
A Downing Street spokeswoman said: "The president is the prime minister's opposite number and it would not be usual for the prime minister to meet with opposition candidates while an election campaign is underway."
Hollande was also reaching out to French people living in Britain.
As well as voting in the presidential polls, the 80,000 French voters living in Britain will, for the first time, elect their own representatives to France's National Assembly in June.
A new constituency for northern Europe covers 10 countries, but the majority of the voters live in London.