I'm from the Netherlands, so yes, I definitely have. I've been to the UK three times in my life. Once to Scotland as a little kid, so I don't really count that. Then I went again about 5 years ago with my family. Then the last time about 3,5 years ago, I went to London on a school trip. Great fun!
I also went on vacation to Belgium about 2 years ago with my family. The next time after that was a weeklong school trip to Berlin, Germany with school. Easily my favourite school trip ever. Highly recommended to visit at least once.
The last time was my scouting camp to Luxembourg last summer. I had a ton of fun there as well. Easily my favourite (though to be fair, that was mostly because I just had a ton of fun with my friends).
So to summarize: UK (2-3 times), Belgium (once), Luxembourg (once), Germany (once). But then again, all of these countries are right next to the Netherlands, and the Netherlands isn't that big of a country, so I guess it's a little easier for me to take a vacation to another country than for someone from the US for example.