Real Estate / Capital gains on Poland property - tax query? [6]

I am a polish national who purchased a property in Poland in 2006 sold the property 4 yearslater which is in 2010.The money I made on the property I spent to purchase a flat in London. I assumed that since Poland is in European union I will not have to pay capital gains tax as I bought another property of a higher value. Apparently however that's not the case.

Can anyone please advise if that is the case and if so what tax I am liable to pay?