News to be announced within a few weeks: new base at Amsterdam Schiphol Airport. Ryanair set to take off from Schiphol - NL Times
My guess is they will either head to head with easyJet on the Amsterdam to London routes, either from Luton or Stansted.
Prepare for it to get messy and the bottom to fall out on ticket prices!
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I wonder how the taxiing and turnaround situation will suit Ryanair at AMS, depending on the runway you land on, you can regularly have a 20 minute taxi to the gate. This eats into valuable to turnaround time.