Well, it turns out I can answer some of my own questions after some further research and a bit of work on the vehicle. I just thought I'd post some more here in case it's of any use to anyone else. All of the following relates to point 1 in my previous post - the immobiliser coil.
Firstly, 95401-1H000 is
the correct part number if your key barrel is lit with an LED. You get the coil with a length of cable terminated with pins to fit in the 6-pin connector (photo 1)
I paid GBP 23.17 + VAT.
This part goes on to answer several of my related questions. You don't absolutely need to remove the microswitch on the barrel, as you're simply (ha!) replacing the 2 pins in the plug (black and white wires) for the coil. However, I *did* choose to remove the microswitch as I needed better access to the plug.
The pins are unlike any multipin plug pins I've ever seen before. They don't have a retaining tang/tab on the metal pin; instead having a plastic retention latch/step in the plug. It turns out they're special KET Korean connectors. I found them quite awkward to remove, but once you know how to do it, they're quite straightforward.
Replacing the immobiliser transponder coil - 2007 Ceed 1.6crdi - Steps:
1) Remove steering column cowl (and lower dash panel if desired for better access). One screw under the cowl, and two behind the steering wheel (turn wheel to access screws). The lower dash panel is secured with 4 screws (2 behind the fuse cover) and clips.
2) Unclip and unplug washer switch stalk (RH stalk) for better access
3) Disconnect 6-pin connector to coil, LED and barrel switch
4) Remove coil securing screw - the coil/LED will now slip off the barrel
for easier plug access
5) Insert key and turn to ACC. Depress retaining pin underneath the barrel and gently remove the barrel and key. This will bring the "key-in" microswitch with it. photo 2
5a) I chose then to remove the microswitch from the barrel so I could lubricate the barrel mechanism with some graphite and the microswitch with some silicone grease, as it has stuck a few times (which disables the remote central locking as it still thinks there's a key in)
5b) Put a small screwdriver under the microswitch plunger and push it off the barrel (away from the keyhole). This is a bit awkward, but won't need much force, so be patient - it will slide off gently once the plunger is out of the way. photo 3
. Now you've got the electronic gubbins separate and you can take them somewhere more comfortable to work with.
end of easy-access barrel bit
6) Dismantle the coil / LED assembly. The LED twists out, while a small screwdriver under the retaining clips will part the LED holder from the coil.
7) You now need to remove the pins for the black and white wires, and replace them with the ones for the new coil. This needs you to overcome two retaining devices:
7a) Remove the plastic pin retainer clip - a small screwdriver and gentle levering will do here. You're likely to mark the plug a little doing this, but I couldn't find a nicer way. I found levering at the right-arrow in photo 4
the most productive
7b) Remove the relevant pins. You'll need a very small (1-1.5mm) flat blade to do this. You're aiming to push the blade right along the top of the pin until you hit the plastic tang and then gently lever it up. While doing that, pull the wire, and if you've got it, it will easily slide out photo 5
7c) Replace with the new pins - I don't think black/white matters, but on mine, black goes adjacent to the yellow/red tracer wire. The new pins will simply push into place, with a click once they're located.
7d) I then liberally coated everything with silicone grease before replacing the plastic pin retainer. I found that it goes in at a slight angle (lower towards the cable exits). Push firmly to reseat it photo 6
8) Reassemble the coil / LED holder assembly. It clicks together; reverse of removal.
9a) If you dismantled the barrel microswitch, route the wires neatly before you pop the microswitch back on the barrel. It's a lot easier to refit than remove! Line it up with its slot, and push it towards the key end. photo 7
9b) If you removed the barrel from the ignition switch, insert the key, turn it to what would be the ACC position and gently offer it back up to the barrel. You'll need to line up the "key-in" bar with the slot in the ignition switch and then gently push it home. If it doesn't go very very easily, check the key is at the ACC position and try again. photo 8
10) Offer the coil/LED assembly back up to the barrel. Check the wiring routing (see step 9a!), and if you're happy, insert and tighten the retaining screw. photo 9
. It's worth pointing out that I'd not got the LED/coil cover clipped back in properly in photo 9. I went back and did that
11) Reconnect the 6-pin plug.
12) Refit the cowl and the lower dash panel (if removed)
Hope that is of some use to someone!
Regarding my question 2 from the previous post (the SMARTRA unit P/N: 95420-1H700) - as that's next if the new coil doesn't sort it(!):
a) I've since found several references to where the SMARTRA unit (between coil and ECU) is located. This ranges from on a bracket between the accelerator/brake pedals to somewhere up in the heavens behind the instrument panel. I have looked and looked and reached and reached but cannot find it. I haven't had the entire dash off, but have had instrument panel, lower dash, and dash reinforcement out, and the nearest I've come is a relay-type thing (P/N: 39510-27010) up behind the instrument panel (from below) near where one source suggests it should be.
If anyone can help me out there, please do!
b) Just for anyone considering DIYing the SMARTRA unit, several sources suggest that despite this being simply an RF/digital translator, it does need the keys re-teaching so it can exchange an encryption key with the ECU - so you'll need GDS or HiCom. I guess that would rule out second-hand ones unless the seller can guarantee they've "neutralised" it.