Onto France For Next Election

So the media circus has packed up its equipment and moved on to France where the next important election is due to happen and although they don't have a candidate like Donald Trump, they do also have a right wing racist just as vilified in Marine Le Pen of the National Front.
The spotlight at the moment is on Socialist Party candidate Benoit Hamon who has suddenly risen up from the pack to comfortably win the first round primary and now faces a shoot-out with Manuel Valls for the Socialist Party candidacy.
François Fillon of the Republican Party is favourite to take the Presidency but Benoit Hamon is being labelled a dark horse and he does have the momentum mainly due to an idea that seems to be growing in popularity globally, universal payments.  
The idea is that each citizen receives a monthly payment regardless of employment or income with Hamons proposal that by 2022 every French citizens will receive €750 a month which works out to approximately £650.
I understand the argument that it would eradicate poverty and free people to do what they want but struggle to get my head around how this could possibly work and critics have estimated its would cost between €300-€400bn.
A 2012 affordability study done in the Republic of Ireland by Social Justice Ireland found that basic income would be affordable with a 45% income tax rate across the board to continue to fund all current government spending with savings coming from government offices that would be made redundant such as Social Security and reduced Government costs such as Health as conditions related to poverty would be less common.
I'm not sure about it as it falls entirely on people working and paying the 45% tax and with an income guaranteed of £650 then people will work less hours therefore earning less and ultimately paying less in tax which would have to used to fund the program.
Hopefully, if Mr Hamon wins we will get a chance to see it in action and if it works it will be adopted elsewhere but if it doesn't then France is going to be in for a hard and very expensive fall.