I took a day trip a month or so ago to Boulogne Farmers Market, I highly recommend it. Took an early ferry (7:30am ish) over to Calais followed by a short 25 mins drive along the coast to Boulogne Sur Mer, arriving around 10am French time. Parking in the centre of town in a nice new underground car park was about £3 for the whole day. There is a farmers market every Saturday which runs until about midday. Amazing fruit, veg, meat, fish, eggs and of course cheese, all locally produced and at great prices. The people were very friendly and welcoming despite my terrible attempts at French. The town has few high end cheese, chocolate and wine shops if you're after something special but they're expensive, similar or maybe more than London prices (exchange rate doesnt help). We grabbed a nice lunch in town took a short drive to the massive Auchan hypermarket where we stocked up on cheap wine and more food. Returned to Dover by about 5.30pm. Amazing and super easy day out. There's also a beach and aquarium in Boulogne if you want something different to shopping. We'll definitely be going again.
If we leave the EU you can be guaranteed the UK govt will impose limits on how much booze you can bring in - like they do with every non-EU country. The advantage of Calais is that tax on wine in France is so low compared to the UK so you can save a fortune during a day trip if you buy in bulk.
Do we get Duty Free again if we leave the EU?
Calais was a lovely town with lots of good shops and restaurants. I haven't stopped in the town in recent years, but as this deal mentions vehicles, it might be best to think of it more as a trip to the shopping centre and hypermarket. A shame for the residents and retailers of Calais town centre, but I can't see there being a lot of demand to 'download our two hour walking tour'.
Don't go then, leave all the bargains to me, and plenty of others. I travel through Calais a lot and have personally had no problems. Of course some people will have had 'experiences' but you may as well give up crossing the road because 'something may happen'. Can be a good day out, lots to see and do. Plus, the bonus of some shopping.