Just back from our mini-tour of the North Sea route; I'm sure the other half will post his impressions at some point, so I'll just add:
the Stayokay hostels generally have good secured bike parking - keycard entry sheds with fairly basic racks. If you lock your bike up at all, it's more secure than 70% of the bikes in Holland already.
nicely stocked bike shop in Haarlem, Bike Planet (website in Dutch), worth a look if you're passing.
watch out for mopeds on the bike paths. My one scary moment came when I was doing a fairly stupid overtake on a bend and nearly crashed into one headfirst. My bad, but still... mopeds?
If you get the Stena Line overnight ferry, take earplugs. The wakeup call is blasting 'Don't Worry, Be Happy' on the tannoy at 5.30am. Bastards.
Just back from our mini-tour of the North Sea route; I'm sure the other half will post his impressions at some point, so I'll just add: