knx-universal-dimmer able to control 230v Dimmable LED-lights (or other inexpensive solution). I've come cross a, hopefully, relatively cheap and hopefully high quality seller of LED-products (downlights, gardenlights, downlights with GU10 fitting) all dimmable and at 230v.
The MDT stuff should work. Get one, with return guarantee, and test it. I personally don't like 230V LED stuff.
Blind actuator to control motorized projector screen and pleated blinds. Is it possible to control several blinds with same output?
Same here. I have MDT and like them. You can control several blinds with one output, but you need a relais in between. In the end, I decided to control every blind individually, but group them with LinuxMCE. However, I would not try to control a motorized projector screen with a blind actuator, as the blind actuator is not exact enough.
Binary inputs to be able to connect movement sensors, light sensors and leakage sensors I guess still the cheapest way to control these things is to buy non-knx and connect to binary input, right?
I have KNX PIRs as you are able to get more than motion, but also light intensity setup automatically. Apart from that, if you really want 1/0 only, binary inputs are neat. Some binary inputs only have problems with accepting higher frequency inputs. So if you have stuff that changes rapidly, and you want to count that, make sure your binary input supports it.
Apart from that, one word of advise, IF you have a significant other: Make sure your install works without LinuxMCE. It is okay, that timed events don't fire without LinuxMCE, but not being able to turn lights on/off, or opening/closing blinds without LinuxMCE running, is a recipe for trouble in the relationship.