That's not what your link says. It says that the countries in the EU will lose around 1.5% economic output, not growth. Britain is already about the slowest growing developed economy going, I'm not sure we should be rubbing our hands in glee if other countries start to decline.

Your link seems to suggest that the mean value to EU countries of having Britain as a full partner is only 1.5% of GDP.

Any idea how much GDP Britain is expected to lose upon exit of the EU?

Your attitude very much reeks of cut my nose off to spite my face.