If you plan to visit the UK and Schengen countries on a single trip, ALWAYS apply for your UK visa first.  UKVI keeps the passport for the entirety of the visa process and there is no visa status tracking. Calls and emails to customer service are charged. Even if you pay and contact, you will usually get a canned response. If your UK visa is refused, there is no "appeal". You can only re-apply, which means you have to repeat the entire process again. On the other hand, the Schengen visa application process is much streamlined. There is application tracking, customer service and appeal.  I highly recommend applying for your UK visa first and get done with it. After that, apply for your Schengen visa.  When applying for your UK visa, show a "UK-only" itinerary for your UK visa. This eliminates the need for submitting your Schengen visa, flights in/out of the Schengen region, etc.