Two things that might be useful to know:
a. The Koksijde CTR might also be active, but to a lower limit that's depicted on the chart. Obviously Ostende APP will know whether you need a clearance through or not.
b. When flying from Belgium to the UK, Ostende APP by default seems to arrange a "handover" to London Info (insofar a "handover" to an INFO frequency is possible). Who are happy to take your position report and will ask you to report coasting in over DVR. But Manston is actually able to provide a LARS service in this area as well. Next time I'm going to do the crossing I'm going to try Manston first, London Info second.
Furthermore, have you crossed considerable bodies of water before? There's an effect you need to know about, and have a strategy to deal with it. At FL45 or so, you will find that the grey-blue of the sky seamlessly blends into the blue-grey of the sea, leaving you without any horizon. Even (or maybe: particularly) in CAVOK weather.
The solution is to go on instruments or look straight down to see waves, boats and other stuff that will give you a clue as to your attitude. I happened to be in an aircraft with an autopilot and simply switched that on.
It's not particularly dangerous, but it is something that you need to think about beforehand. And if you find you really can't hold a proper attitude, TURN BACK and try again at a lower altitude. At a lower altitude the distance to the horizon is closer and this effect is less pronounced. But obviously you'll be out of gliding distance from land longer.