Assuming you're flying through Schiphol airport, it has the airside transit, so you will not need to go through Schenghen area. All UK flights in AMS depart from a non-Schenghen zone (D-E-F-G gates), as well as the rest non-Schenghen flights. You'd only have a (rather long) walk from D gates to F gates or so.
As @phoong mentioned in comments, this only applies to citizens of the countries who do NOT need a transit visa for Netherlands. Saudi Arabia citizens do not.
Also, while this is the case with Schiphol, this is not the case with all airports. For example, my flight from Bucharest to Berlin (TXL) dumped us straight into the passport control, even though my next flight was outside EU, thus requiring me to go through passport control twice.
Regarding H/M gates mentioned below, there is a passport control booth, but an hour ago it was completely ummanned, so my idea of asking them how it worked failed. Most likely it worked similar to many Asian airports, where a passport booth is only manned when the gate is turned into "international" (in this case Schenghen) departure, and otherwise people just go to the gate without passport control.