Now, he has had a quote for £3k and I am thinking that this is rather
a lot for the size of the job. He was also told that there is 2 weeks
worth of work.

There is more work in a French installation compared to a UK. This is for
several reasons. For example, the lack of ring mains requires the
installation of more socket circuits. Also, due to termites and other
nasties, you can't just lay cables under the floor, they must be protected
in conduit. There is almost certainly an extra 16 layers of bureaucracy
involved, too, all requiring palm crossing.

Christian.