And in that case, Brexit can be proven to be working well for Britain as the country will not anymore be dragged by the weakness of Euro
UK never used Euro. UK uses GBP. They were never really part of EU. It was the last time for them to decide if they want to be in or out. Being a bit in and a bit out was dragging EU back for decade.
Does that mean that countries which did not accept EUR are not really a part of the EU? If it's so, there's a lot more countries like that within the EU.
I've started to expect the fall of the EU when countries that were supposed to accept the common currency did not do it. Later, we've witnessed a big clash within the EU when Germany and France wanted to open their borders for migrants, but Hungary and Poland opposed them. Italy and Greece initially followed the plan but then changed their minds as the migrants flooded the gates.
IMO they should have stopped at Schengen and keep the open borders without trying to establish a central government and a common currency.