We always stay at Bearsted Caravan & motorhome club site near Maidstone. It's 2 minuites of the M20 with easy access. You are only 3/4 of an hour from Dover port. If you can get across the channel in the same day, you could park up in France. There is a shopping Mall on the outskirts of Boulogne-sur-Mar on the N42 off Route de saint-Omer.. You are allowed to park in the car park with no problem..! Macy Dee's is right there too if you fancy some junk food..! Happy travels..
The Caravan and Motorhome site at Maidstone is in a great position. Just off the M20 at leeds Castle services. Back on motorway in the morning within 5 mins and about 35 mins then to Dover. Alternatively, there are some nice offcthe road lay by's between Folkestone and Dover on the cliffs. But they get full with lorries quite early. Then marine parade in Dover, they allow motorhomes to park on the street there, less than 2 mins from docks. You can walk into town for fish and chips etc. Only thing to be aware of, you must go in and out, by the road down the side of the flats