Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Plymouth to Cologne as you normally would.
Located just 9.5 mi from the city center, Cologne Köln/Bonn is the airport most travelers will use when flying to Cologne from Plymouth. Booking flights from Plymouth to Köln/Bonn (CGN) should be relatively easy as there are 0 daily inbound flights from Plymouth from 1 airline.
This flight path from Plymouth to Cologne Köln/Bonn was viewed by 13 users in the past month. Keep an eye out for changes in search interest prior to high and low season.