Okay, sorry for the ridiculous delay. Having had them fitted for a while I'm happy I got them. Though firm I find if anything I prefer them from our point of view as they don't extend as far forwards, and because of the zip-up covers they aren't at all obvious. They made our long trip far, far more pleasant for our daughter, and hence us, and we've used them a few times since on short trips when we haven't wanted her to fall asleep at the wrong time. Anyway, here's a quick guide to fitting...
Remove the existing headrests (just press the button on the seat where the pole goes in and lift the headrest out)
Remove the seat backs - there's a flap at the bottom that clips on to the base of the seat, then they have hooks over a bar at the bottom of the seat back and clips at the top. The first one I think I removed by lifting the bottom up (flexing the back) until the hooks cleared but I was never able to replicate this and ended up using largely brute force at the top so the clips slid out of the backs. No doubt there's a better way to do it!
Remove the centre console - there are instructions here somewhere, but a condensed version is:
Remove the carpet from the storage compartment behind the handbrake lever and remove the 2 bolts.
Unclip and remove the gearstick gaitor (the material bit around the stick).
Unclip and remove the gearstick surround (the plastic bit - you'll need to undo the connector blocks for the power sockets and ipod/usb ports)
Undo all the screws (sorry, I can't remember how many there are, I can say there are 2 right at the front under little flaps that can be lifter with a small flat-head screwdriver and at least 2 under the gearstick surround you've just removed)
Thread the cables for the DVD players through the holes where the headrest poles go (just the short ones attached to the players). Decide which connections you want - I connected the AV-out from one to the AV-in of the other so the same DVD could be played on both screens. Thread the required longer cables from the centre console to the seat backs - I found it easier to go this way than the other, as I could push the cables under the carpet to where the air-con vents come out under the front seats (did you know these were there? I didn't!). I then ran the cables through the loop holding the seat sensor cable and up in to the seat back (on the opposite side of the seat to the centre console), thus not having to make any new holes in the seat. Connect these cables to the ones coming down from the players, and fit the poles in to the seat so the new headrests are in place.
Decide where you're going to put the fuse boxes. I went for the gap in the centre console between the cup holders and the storage compartment. That was plan B, initially I tried under the handbrake lever (as in the picture) but it fouled the lever! Run the power cable from the front of the console to here - I went for a plug so we have control over the power, and so I didn't have to touch the car's electrics, but I believe there's a point available around where the power socket is that provides power when the ignition is on.
Connect up the cables as required, i.e. power to the fuse boxes (solder them or use a standard electrical connector block) and in my case one set of AV-ins to a set of AV-outs. If you get the power socket adapter as I did it replaces one of the players' power cable. At this point you can check everything works!
I bundled up the fuse boxes and the connected cables in a little bag I fabricated, to make them easier to manage. It was then just a case of putting everything back together. You can put the surplus lengths of cable in to the backs of the seats, ensuring there's enough slack to cover the entire movement range of the front seats.
I think that's it, I'm afraid it's all I can remember. It took my Dad and me about 3 hours I think, but we weren't rushing (until the very end when we started to run out of light) and it could be done considerably more quickly, especially if you get a good guide to removing the centre console.
