DHL has produced a rather interesting interactive map of where you might be selling to. They examine the various difficulties and opportunities via an interactive map.
You can find that here. (The above graphic is a screengrab.)
The considerations regarding online selling are in flux. The EU was a no brainer option, and probably does, on some levels, remain exactly that. The UK won’t be leaving the EU any time soon. And likely no time before Spring 2019.
But the weakness of Sterling, post the Brexit vote, does make some other markets more interesting. Canada and the USA, in particular, do have greater possibilities.
Indeed, the EU as a whole does have interest too. In any case, this interactive map from DHL will give you a stack of detail. Look it up.