The EU and Ireland after Brexit: In conversation with former European Parliament President Pat Cox

As the United Kingdom faces a divisive but potentially decisive election framed around Brexit, the European Union is contemplating a future without the UK. 
 
If British voters back Prime Minister Boris Johnson's Brexit plan, what sort of future relationship will the EU look to build with the UK? What will be the impact on Ireland and Northern Ireland? And how will Brexit affect Australia's ties with the EU?