In the Netherlands there is only one dedicated 'Northern Soul' night - the Amsterdam Soul Club, which plays a bit of everything.
There are numerous other nights across the country and these are typically cross-genre events offering a mix of soul, ska/reggae, R&B, garage in varying degrees.
One thing that became very quickly apparent when I moved to near Amsterdam from London five years ago is that the majority of punters attending Northern Soul nights, or indeed even mixed genre nights, are not what you might call lifestyle fans - they're basically just people off the street who go to a club for a good time.
The exception is the ska/reggae scene. The Netherlands has a far bigger ska/reggae culture than it does Northern Soul.
Having said that, there are quite a number of very serious and knowledgable soul collectors - Hans and Harry of Fingerpoppin' Soul fame immediately spring to mind. The distinction here is that these people are soul collectors, not Northern Soul collectors.
Very few here suffer from genre-specific tunnel vision. As an example, in a couple of weeks an event takes place in Amsterdam called "Mods versus Rockers". This is an event where both broad churches come together and share their musical and cultural passions. Scooters will be parked alongside classic motorbikes.
Eindoven is home to the Endless Memories events. They organise regular cross-genre nights that includes Northern Soul. They're holding a weekender in October, a ska/reggae specific affair.
All-in-all, it's a mixed bag...