You could have the world's second largest reserve currency, the Euro. But I'm sorry but from the outside looking in you're not much of a global power anymore. The only thing keeping you relevant are seemingly your armed forces. And on that front France gives you a run for your money.

I'd also bet money the EU would want you back, remember they weren't the ones pushing for a no deal brexit. However terms will be less favorable than last time.

Sorry for being harsh. As a Swiss I get the wish for being independent and having your own currency and freedoms. But let's face it... My gov. Also overestimates our importance and the leverage we have.