Advertising a route to Chateauroux to the general public in Essex or London is likely to represent wasted money. Very few people in the UK have heard of the place, let alone would consider going there. IG Avion have for the last few years focussed on taking people in rural 'middle-of-nowhere' places in France with poor train connectivity to leisure destinations (Nice, Corsica, etc) for a holiday.
Marketing spend should be focussed almost entirely on those living in/near Chateauroux and possibly also Brits with a second home in France