Hi taoball,
If you are supplying software and a software support service B to B then this should come under the General Rule of Services when determining the Place of Supply.
Please see the guidance below:
6. The place of supply rules for services
You do not have to get the customers VAT numbers although you do need to be satisfied that they are in business.
It is your decision as to whether you establish a base in France.
However for the purposes of Place of Supply you do not need to for your services to be deemed as Outside the Scope of VAT.
Thank you.