I recently moved to France from Spain & found buying a bike extremely difficult. It's easy enough to spend money but finding a bike to test beforehand is nigh on impossible. I'm in the south & it may be different in the north but down here there's none of the huge shops you find in the UK. No
Evans, Edinburgh Bicycle, Dales et al. As others have said though, all the big online retailers you know already do deliver to France & for quite reasonable rates too. I ended up buying my Cube hybrid from a company in Germany & there was no postage charge at all.
Having said that, I note you're looking for a road bike. There's far more of those in local shops here than you tend to find in UK shops, as compared with mountain bikes for instance. It's maybe something to do with the generally far superior road surfaces you'll find in France. Every decent-sized town will have at least one bike shop but although some do sell bikes they tend to major on components & repairs.
In my particular case I had no intention of buying a bike here. I owned a very nice mountain bike that was being moved to France from Scotland with the rest of the household. Somewhere en route it went 'missing'. The insurance did eventually pay out quite handsomely but it was a stressful few months.
If I were in the UK, knowing what I know now, I'd buy in the UK. I'd also bring the bike to France myself and not trust anyone else.
If I can be of any more assistance please feel free to ask & I'll try to help. Good luck.
P.S. Where are you looking to move to?