At some point the exchange rate falls and suddenly no one is happy with it either. Recent examples are China, GB, Brazil, Venezuela.
The truth is - as with your comment - a surging/falling exchange rate is neither good nor bad. It has positive and negative effects and things will balance out.
Or to say it differently:
An exchange rate is never low, nor is it high, it is precisely where it should be. - Gandalf the Grey
In this case the other countries are dumping GBP because they think the UK economy will become weaker. That would be like a Sales because your product is flopping.
Same effect, difference cause. One is voluntary on the country/company term, the second is forced by the other actors of the market. The fall of the GBP is significant. The rest of the World is shorting the UK right now and that in itself can be what pushes the UK economy in danger zone.
"That pattern is however a rather unbalanced one, the only sector of the economy that continued to grow was services up by 0.8%; agriculture, manufacturing production and construction all shrank."
What exactly about Brexit spurred this leap in the growth of yoga studios, burger chains, and Star Trek box office returns (A drop in the GBP, as it turns out, for the latter)? Because it seems like losses in everything else is pretty much what economists expected. Manufacturing declined despite a drop in the GBP.
This might help you see some problems.