Very interesting thread this.
Having spent most of the last thirty years living in a region of France that has increasingly supported Le Pen, I can categorically state that this support is due to the very same concerns that exist in Britain. Whilst France is not losing it's identity by any means, a large percentage of the population feels this to be completely true.
The Front National's showing at the last two elections is no more than a reflection of a disenchantment with their political system (or lack of it) and the feeling of impotence dealing with the EU....sentiments which must strike accord to many in the UK.
My concerns over Brexit are not that Britain may well suffer some adverse consequences from our own withdrawal but that our example to the French, the Italians, the Spanish...and yes, the Greeks - will provoke a drastic reworking of the EU at best and the destruction of the system at worst.
Whatever happens, I feel that there's a very good chance that by leaving the club we might actually be creating another one of which the UK should be a member or possibly a new European reality that will take decades of incertitude for the dust to settle and any attendant recession to be over.
It's going to be fun, just not the laughing kind.