I am a New Zealand citizen in a (20 year) defacto relationship with a UK born passport holder.

We have been living in France for the past 2 years and I do not have a long stay visa.

We had not planned on staying so long but it is the way it has turned out.

I did not realise that I was staying here illegally as I am not working or drawing on any social funds. I have recently found out I was mistaken.

When I first arrived in France 2 years ago they did not stamp my passport at the airport.

We are planning on going back to NZ soon and I am nervous about flying out of Paris. Will they realise I have been here this long? Will they have a record of my arrival as my passport was not stamped whe I arrived. If so, what are the consequences? Would I be better off flying out of another country such as the UK?

We have a house in France and are hoping to return for another long term, this time with the correct visas!

No problem on your departure, but you won't be able to return to France again. Before leaving, consult local immigration attorney and find out what to do in order to come back.