I also use Redhill a lot and as SB points out the are great if you want to park up and leave. My last trip to the states recently they charged me £25 for landing and a weeks parking. Service is great. I would never consider flying into Gatwick and parking for a week. The parking at £14 per hour alone would be enough to deter me!
But it does have it's merits when collecting or dropping people off for flights as the handling agents have there own security so will check the passengers onto the connecting flight without leaving airside. I was in Canada last month and the Maldives this month and both times the queue to get through security (not check in just security) was FOUR hours....
It also has the advantage that I can go IFR so 95% reliability.
Schiphol is €180 for a weekend, it has it's own GA terminal and the standing joke is that it is cheaper to park your plane than your car! They are a great bunch. I lived in Amsterdam for many years so it is still a second home for me.