Why doesn't Great Britain participate in the euro monetary system?

Control and History. Being in the Euro means your currency is in collective control. You cannot manipulate your monetary system in areas like interest and manage inflation on your own. The main reason the referendum got voted down was people didn't want to give up their pounds. Nothing to do with exchange rate, because in the conversion process, an agreed rate of exchange will be given. It will never be a case of one pound to one Euro. It was 1.4 DM for 1 Euro when it was converted.