hi! could you clarify: do you mean World War I?

The difference between Britain and France concerning the mobilization ( if that is what you are asking about ) is that Britain needed to rely on volunteers while France on the contrary ordered a general mobilization.

So in August 1914, France ordered 3,780,000 men to join their affectations ( including the professional army ). Farmers were taken out of their fields and sent to their regiments and choice was not given to them.

However, there was a certain enthusiasm similar to the huge success of calling volunteers in Britain.The French government and authorities had estimated some 13% of the men called to refuse and become insoumis ( insubordinate ) but the numbers show that only 1,5% of the men refused and fled the mobilization.

Source : 14-18, retrouver la guerre by Annette Becker and Stéphane Audoin-Rouzeau.

So yes, Britain relied on volunteers at first while France did not and decreed a mobilization of men.

Though I can't confirm you for Britain, I'm sure I read in Kitcherner's last volunteer that Britain did rely a lot on propaganda. The public opinion was of outrage when Germany entered Belgium, a neutral country. This feeling was of course fed by the media of the time.