The basis of wiring regulations in all EU member countries will be firmly founded on technical documents issued by CENELEC. These harmonised documents must be referred to in any national standard and anything that might conflict with them must be withdrawn from that national standard. Harmonised documents will pave the way to a reasonable level playing field under the new approach methodology.
The issue with BS1363 sockets installed in a French house is an interesting one. Should I choose to install say a typical French socket outlet under IEE Regs in the UK, I think that if objection were raised I think that I could successfully argue that the IEE Regs (BS7671 2001) would, by reference to the acceptance of European Norms, permit such a situation. However, I have no doubt that the more than your jobs worth brigade would be out in force.
In any event, I think in due course the UK socket may end up in the same grave as the British pound!