Netherlands Campervan Hire - Local Costs and tips?

[CamperVanner]

What does it cost to hire a campervan locally in the Netherlands?
Are there plenty advertised at Amsterdam airport that you can just call up
and not have to book ahead, what with the GFC and all?
One with a shower and toilet that will accommodate two people comfortably
but us usually advertised as a 4 berth, which is really rubbish if you want
any comfort. Typical 2 to 2.5 Litre diesel rig, for about one to three weeks
is what I will want.
They are advertised for around E97 per day on websites like this

http://familycampervanhire-holland.com/index.php

Are there better deals available and can anyone list some URLs please?

Although we live in Australia I have previously owned a campervan in the UK
and toured Europe seasonally for about five months annually for five years,
but sold it a couple of years ago. I want to buy a canal boat in the
Netherlands to spend a few years touring the French canals, and will need a
campervan to tour various boat brokers, particularly in Friesland, and it
seems that a campervan would be far better than getting a car and using B&B
accommodation ,which would cost about E50 a night for B&B and probably at
least E30 a day for a small car.

With all the crap that campervan companies carry on with about payment in
advance and no refunds, what I want is to just be able to call one up when I
get to Amsterdam and hire a campervan on the spot or within a day or two,
pay for a week, and extend it longer if they have the van free, so I haven't
booked and paid for a van for three week, then find a canal boat after a
week and waste several weeks canper hire.

We have vast experience touring Europe and the UK in our own canpervans
since the year 2000, but I have never hired a van in Europe, having had our
own van, so I would appreciate any tips from those in the know. Being a
disciple of Scrooge McDuck I don't want to go the mugs way of booking and
paying in advance for something I may not need for more than maybe a week.