Hi,
We do not do something specific for US or France. The documentation of Paypal Adaptive does not talk about anything special for countries. I want to say : on the contrary, it's more an open API.
The Paypal UK page is the same than the US one
cms.paypal.com/uk/cgi-bin/?cmd=_render-c.../e_howto_api_APIntro
NOTE:The application owner must have a PayPal Business account. Senders and receivers can have any PayPal account type. Senders and receivers are not required to have PayPal accounts initially. PayPal prompts a sender to create an account before a payment can be completed. A receiver must create an account to receive the funds after the payment completes.
There is no country option in the plugin or in the API. I don't know why the payment is not processed but I am not sure that there is something special to do for such "UK App" (if such special API really exists).
Regards,