As far as I'm concerned the most civilised, cheap and time-efficient way to get to the Netherlands is overnight on the ferry. I left home at 7.15pm and was at Amsterdam Centraal by 10am the following morning. No queuing - I walked straight onto the ferry, enjoyed some food, a bottle of wine and had breakfast the following morning after a good night's sleep in an en-suite cabin.
If you get a rail/sail ticket, you can travel from the Hook of Holland to any Dutch station for just over £100 for two of you, which is excellent value.
Because of this ferry service, the Netherlands have now become my place for a quick getaway. Much easier than travelling there by Eurostar.
Is this your business?