Calais is a convenient port of entry to France, as it is the closest to Dover and the short Channel crossing to Cap Gris Nez, and it still continues to has for inbound and outbound flights at http://www.aeroport.capcalaisis.fr/pilot/ This website also contains the customs notification form.
In 2014 Calais lost its Class D airspace so you no longer need a transponder, but in practice we have found that both Calais and Le Touquet are very pragmatic and have not been known to refuse entry to any WFAeC traveller without a transponder. Calais now has AFIS (in English) 4 days a week (Wed-Sat), and circuit calls in French outside of AFIS hours. The tower chief speaks good English and is very helpful. They are very happy with formation arrivals (March 2014).
There is Flight Declaration form on the airfield website, which serves to advise French Customs of arrivals from the UK. For most pilots, this form is a convenient form of request. It must be completed at least 2 hours before departure from the UK.
The airfield is out on the east side of Calais at Marck, and it's quite a long taxi ride into town. Marck town centre is just 5 minutes walk from the airport and the No 1 local bus leaves from the square in Marck, costs just €1, and runs every twenty minutes to Calais and the CitiEurope shopping centre. The town is better than one might suppose - good array of bars and restaurants - but Calais probably isn't a destination in its own right, more a place to get the paperwork done or, if the weather turns bad or doesn't favour a channel crossing, somewhere to hole up until conditions improve. We stayed at the Hotel Jacquard Calais Centre (which was previously part of the IBIS group) which is well positioned for the town centre and more than adequate at a relatively modest cost. (RG 9/2009). There is a regular bus service between the airport and the city. At Feb 2018 here are links to the route and timetable. These may not be current when your read this.
Another visitor writes: "Calais, also known as Aeroport International Calais-Dunkerke, Aerodrome Louis Bleriot Aerodrome and Aerodrome de Marck. Calais needs to attract more business and staff do make an effort to provide a good service to visitors. This is a good port of entry and departure. On 19th May 2013 I managed to land, refuel, file a flight plan and leave in the space of half an hour !"