As long as you are in Belgium at the time of your subscription (given that Spreds only does marketing in Belgium), you can invest if you pay taxes in one of the following countries.
European Union
Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, and Sweden.
EFTA member countries (EFTA)
Iceland, Lichtenstein, Norway, and Switzerland.
European micro-states
Andorra, Lichtenstein, Malta, Monaco, San Marino, and the Vatican.