Bearing in mind that a question like this can raise very subjective answers.
You will find that service stations in Holland can be just a garage they do however normally have a counter that will make you sandwiches while you wait and very nice coffee.
Belgian Services are adequate but average but most do seem to be getting refurbished.
If you let on where you are going too I will probably be able to point you in the direction of a good alternative to service Stations without going too far off route.
To be honest they are all probably on a par with each other.
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