I was in France 2 weeks ago and can only tell you what i saw - no Hi Viz on bikers at all until we got close to Calais then we saw a few UK bikes heading South East with Hi Viz but no French bikers at all.
The Government supposedly released a statement last week saying that their intention was never to introduce mandatory Hi Viz jackets but instead to make the wearing of "reflective bands" compulsory. (again this is not clear if they mean Hi Viz Sam Brown belts or just reflective piping on a jacket for example.
We will have to wait and see.
Lots of Bike Cops about the 2 weeks we were there and not one of them had any Hi Viz - you would expect the Law to adopt the Law earlier than anyone else?? So I wouldn't worry about it but I still think it is a good idea to carry a Hi Viz vest with you - amazing how much more visible you are if you are stood at the side of a road waiting for help......
Rik