As shown in Cameron's [white paper on Brexit from last February](https://www.gov.uk/government/uploads/system/uploads/attachm...), the critical part of the exit process is to buy more than 2 years to define the new relationship (article 50 has basically only this period as a hard fact).
The paper does bold that a realistic timeline would be ~10 years. Meaning the UK needs to find bullet points to negotiate additional time... with all the free goodies of being still a "passive" member of the EU.
So they're buying 4 months now. They need this to understand their leverages, friends and foes. Many in Europe will be receptive on avoiding a clash. Merkel right now shows signs of resilience.
Make no mistake: part of the City and tech industry sees a strong potential in Brexit - as long as there is no "free fall" period after 2 years.
Everything will be about buying time.