Hi Marc,
I agree that you shouldn't shy away from using lots of oil....either in the curry base, or in the final curry. As others have said, you can always skim off any surplus oil prior to serving.
As an indicator, I use 700ml of vegetable oil in my curry base (to make 7 litres) and about 150 -200ml of vegetable oil in my final curries (to serve 4)
I never remove the oil from my curry base, before blending it, either (assuming you can actually even see it!). I find that the oil (from the curry base) rises to the surface, when I'm cooking my final curry, anyway.
One other thing I believe is important. The oil will not rise to the surface if you don't cook the curry for long enough and/or cook it at too low a temperature. There will obviously be a trade off between time and temperature.....i.e. higher temperature, shorter time and vice versa.
When frying spices (paste) the oil rising to the surface is a good indicator that the water has been driven off and that the spices have been properly cooked. It should only take a couple of minutes on high heat......longer on medium heat.
...I think this is probably why Darth has success with cooking his curries in an oven....
so:
- lots of oil
- lots of heat
- sufficient time
Hope this helps!?

Regards,