Brexit won’t happen. Fear is too powerful a force. But, anyway, it’s in Britain’s best interests to remain in the EU. It’s also in Ireland’s best interests, along with the rest of EU.
If Britain were to leave the EU it would disallow free trade between Britain and the rest of the EU members. It might be seen as a reason for companies to think twice about investing in Britain. Sure, Britain would still be a big market on its own, but it would make things more awkward and complicated for companies to set-up there because of Britain’s laws being out of kilter with the EU laws.
It would also make Britain weaker as an economy, as it would no longer be part of a very important club. Some people who want Britain to leave want the country to go back to the glory days of British power. But it seems that at present Britain is very far away from that. And I don’t think the British public will be patient with such a project. And I doubt that project would succeed, anyhow. People in favour of Brexit want the country to essentially isolate itself and hope China and others come to its aid. I think that an isolated Britain wouldn’t have a good bargaining position with potential helpers.
Also, if Britain became weaker this would be bad news for the US and many other countries because all these countries benefit from certainty.
It would disrupt the easy-going relationship that Ireland has fostered with Britain. The British would still be our closest neighbours, but psychologically wouldn’t seem to be as connected to us as before. We would be living under EU policy and rules, but Britain would not. They wouldn’t be as European as us. It would be a cultural tragedy.