Hi Bilbo,
I don't own any Panasonic gear, so there could be further advice from people who are familiar with your setup, and can give better advice than me, but I'll do my best.
Connect the component outputs of the dvd player to the component inputs on the tv. Your dvd player and tv are both compatable with progressive signals, so make sure that the progressive option is enabled in the dvd players setup menu. As far as I'm aware, the dvd player only outputs NTSC progressive, so region 2 dvds will not benefit from this option. They can still be watched from the component outputs, but only through interlaced component, not progressive component.
Connect the RGB compatible scart output of the sky+ box to an RGB scart socket on the PD30, and make sure that the sky+ box has been set up to output RGB. Also make sure that the sky+ has been set up to display a 16:9 image (not 4:3).
Connect the non RGB scart socket of the sky+ box to the input scart of the video recorder, and connect the output scart of the video to a free scart input on the PD30. In this way, should you want to tranfer recordings from the sky+ box to VHS, then you should be able to do so. Also, plug the ariel lead into the video recorder, and the RF output of the video into the tv.
All the sound decoding is built into the HT900, so you won't need the optical lead. This lead would only be needed if you were connecting your dvd source to a seperate amplifier/receiver.
I realise this probably sounds a bit confusing (I'm confused

) so if you have any more questions, I'll try to answer them.
Cheers.