I agree, 1 day is not enough data to extrapolate upon, we will have to see how the currency performs as a general trend.
Business on the whole wants us to stay in Europe, so the markets are going to get jittery the more likely a Brexit is.
But at the end of the day, whatever happens, in or out, it's not going to be catastrophic end of the world stuff, we will all get up the next day and everything will carry on as normal. The markets will regain their 'confidence' and business will continue trading, either with a bit more red tape or not. (Personally I'm underplaying that last bit, as someone who worked in import/export before all this, it is so much easier now than it was then, but it still worked and trade happened.)