Flying to Schiphol is very straightforward, but more than a little pricey. The VFR arrival is as you describe, although I have never once either required a VFR slot, or even heard of one being needed.
Handling is by KLM General Aviation
http://www.klmga.nl/
and you can make your request for handling (mandatory) online there. You will provide an ETA (and ETD) for them, and they will sort out any logistics with the airport authorities.
VFR departures from Schiphol to the UK tend not to use the VFR sector, instead, you are cleared via the control tower overhead straight towards the coast, and away, usually below 1000 QNH initially.
By way of hints and tips:
1) Make sure that you are very familiar with the VFR approach sector and fly the procedures with great accuracy. You *will* be turned away if you disregard the procedures or fly them badly.
2) Make sure that you call before startup, and expect to receive your departure clearance before you start engines.
3) Make sure that your checks are complete before you line up on the runway. Dutch ATC tend to think of you as being like a turboprop, and will encourage you to line up and depart before you may be ready. You might want to think about doing the checks on the main ramp (which is huge) before requesting taxi, even, if the presence of other aircraft and people don't preclude this.
4) Expect to pay around 150-200 Euros for a day trip in a PA28 or similar.
Drop me a line directly if you need more specific help