I am a UK based web developer currently building a French language affiliate marketing website to be hosted in France. My business partners are French and I am trying to decide whether my business should be registered in the UK or France. Is there any advantage in terms of SEO if the company is registered in France? What other considerations should I be making.
In terms of SEO there is no difference at all - you can register your company in Cyprus and still have a good ranking on google.fr.
Most of the huge companies operating in France, including Google and Apple, and a lot of little ones, are registered in Ireland, the UK, or Cyprus. They obviously don't have any SEO problem.
The only difference is taxes: it's far more expensive to create and run a company in France than in the UK.
As you are UK-based it is likely that you will find it easier to set up here, rather than in France (or anywhere else). As long as your business partners are agreeable, do it here. There is also the issue of tax, where the UK has relatively generous corporation tax rates, especially for SMEs.