It's only responsible in the sense that it caused the rate to inflate from 1.43 to 1.5 in the space of 10days and aisequently drop to its now 1.33. It's realistically dropped 10points and not anywhere near the 17/18 that some spout FACT.
The rates only dropped due to mass selling and trading in the markets as assets left the UK and UK based investments. If the trading and mass selling of UK assests and UK based investments didn't happen where do you think the rates would be? The rate drop was caused by the uncertainty the government provided by not evoking article 50 and for all issues within and the collapsing of government parties including the resignation of the PM. That is what causes rates to drop not because of brexit as we haven't even left yet so still have all the trading powers and legislations and laws we already had! What happened when I woke up the following day and had to deal in dollars? Nothing. Nothing had changed. The principles remained the same as they always will and do. It's only change was the rate drop and the halt to purchasing that followed. Once stocks ran short and new batches came in at higher pricing (or revalued by distribution) did buying start again as life needs to continue.
Brexit is a term to describe a collective event that has roots in all aspects of life surrounding the date, events and ripples in that period and the time running up to and following it.
You say look at the exchange rates. Look at trading surround the rates and the effect they have on the rates and not the rates themselves. It's misunderstandings like that that drives panic and the ripple touches other people and businesses like dominos being toppled.
Retailers may have said that in June and prices would rise in August but that's just common sense. If the vote is to leave investments will likely leave and the strength of the pound would drop. Less capital in the country means less value which means a weaker currency. You get paid £40k a year before brexit you still get paid £40k a year. The only difference is that the £40k is worth less elsewhere now.
The 5D4 is cheaper. It just isn't here and that has nothing to do with the UK voting to leave, it's to do with the collective events surrounding that decision driven by fear, worry, uncertainty and stupidity. Remove subjectivity and replace it with objectivity and we would likely not have half the problems we have now. Subjectivity drives opinion and objectivity drives fact.