There are, of course, advantages. You'll be able to import alcohol and cigarettes tax free from the UK, but amounts are limited: 1 litre of liquor per person, 200 cigarettes, 4 litres of wine and 16 litres of beer. Carry more and you will have to pay import duty!
But beware importing meat, cheese, milk or other animal-based products becomes illegal.
At present a Belgian ID card is sufficient as travel document. After 29 March an international passport could be required and even a visa. The European Commission has proposed visa-free travel for Britons entering the EU if this is reciprocated by London.
Border checks already exist between Belgium and the UK because the UK isn't a member of the EU Schengen free travel area. Checks could become stricter with the prospect of long queues at Eurostar, Eurotunnel and the airport.
Eurostar is a UK company and will have to apply for a licence after a No Deal Brexit to allow it to transport people in Belgium, France and the Netherlands. The UK hopes to conclude bilateral agreements with these countries to avoid disruption.
European air carriers will have to seek permission to land in the UK and the same goes for the Brits! The UK government hopes any disruption can be limited. People travelling via the EU to a further destination need to ensure more time as luggage will have to be screened again.
Fly between the UK and the EU today and your rights as a passenger are guaranteed and you could qualify for compensation. Such guarantees will only be certain for flights departing from the EU after Brexit Day.
Want to hire a car in the UK? Check if you will need an international driving licence!
Want to use your smartphone or tablet? This will become more expensive because the EU ban on roaming charges no longer applies as the UK is a third country.
Fall ill in the UK and you may need additional insurance to cover medical costs. Check with your mutual or health fund. At present the EU health insurance cards suffices, but nobody knows what happens after 29 March. Using a debit card too can become more expensive because bank charges are limited in the EU.
Whatever your plans, have a great trip!