Is the pound heading towards parity with USD?
Unlikely, but never rule anything out particularly in momentum driven forex markets.
UK has a chronic current account deficit, so to balance out the country spending more on imports than it exports UK historically has had to sell debt and/or assets.
The appetite for UK debt and assets will obviously diminish given the Brexit related regulatory & political uncertainty so the currency naturally falls due to less
demand.This will be partically offset when/if UK reduces imports. The primary driver for this weeks decline is that the "market" realised that Brexit is for real and thus increased regulatory/political uncertainty is now upon us. Large banks/investors up until this week didn't really think anything would change, as historically UK governments have always done whats best for the finance sector and that means remaining in the single market. Large banks/investors now know times have changed.
At some point, maybe now, investors will think the cheapness of the GBP and UK based debt/assets offsets the uncertainty. Nobody knows for sure what that level would be.
Personally, as a dual AU/UK citizen living in London, if the GBP falls anywhere near parity with USD, or AUD hits 0.70 to the Pound then I'll be backing the truck up and buying more GBP denominated assets.
Next 12 months could be a great time for Australians to pick up a nice pied a terre in London!