Just a post of info really.
Laguna II Phase I 'Extreme' 2.0 16v
Standard Rear Speakers - 130mm and separate tweeter (next to speaker)
Standard Front Speakers - 130mm and separate tweeter (on dash)
Fitting rear speakers, using flat pointy object, (I used flathead screwdriver) wedge in and prise off the speaker cover, it doesn't clip in it simply pushes in and pulls off. Comes off quite easily. If you have manual winding windows in the rear you must first remove the winder handle, which just pulls off straight, again I used flathead screwdriver in behind and it pops straight off and pushes back on once your finished.
Once speaker cover is removed, two torx screws hold the standard speaker in place, top and bottom. Remove these, lift out speaker and unplug the standard plug thing you find on most modern cars.
I used an adapter from an old halfords speaker kit I had laying around to connect the new speaker to the standard plug thing (sorry I don't know the term for this thing lol).
Offer up new speaker into hole, two holes there already, should be enough to hold speaker tight with the two torx screws, no real depth restrictions there, its clear behind the speaker.
I didn't change the tweeters in the rear as my new speakers were 2-way (bought in error, thinking thats what I needed)
Front speakers, same procedure, same speakers as standard. Pop off cover, unscrew 2no torx screws, dismantle block connector and use wires or use easy option halfords speaker adapter to connect to new speaker.
I've seen posts about a huge bit of metal behind the front speaker restricting the depth but the Phase 1 Extreme didn't have this bar of metal so the Alpine components I bought had LOADS of room. As rear, I never changed front tweeters but may do soon as they sound absolute cack.
Hope this is of help to some, without a Haynes manual for the new laguna and the car manual saying nothing more than 'take it to a renault garage and have them do it' it's hard to find info on DIY stuff for the laguna. This website is fantastic for getting that info btw, keep it up!