Realistically they are a country of just over 5 million. They are subsidised by England to the hilt, yet its never enough. Free prescriptions, university places etc etc.
Their largest market is England. If they want to go then let em. It really will not hurt England. Many countries in eastern Europe and former Yugoslavia have gained independence this last 25 years. Its never the disaster people make out. You seem terrified of change. Change is very often the thing that sparks opportunities and prosperity.