I need to replace the outside lower seals on the rear quarter windows. I’ve seen suggestions that these simply slide out of the trim piece and the new ones slide in. Can anyone confirm this?
Chuck,
What is the year and model of your Jaguar?
Paul
See the thread title, Paul. 
Yes, you can slide them out and slide in replacements with the trim in place on the car. However, it’s quite a trial fitting the new ones and if you stretch them they can look a bit wavy along the edge that touches the glass. I did it years ago and use a lot of silicone lube which you then need to ensure you clean off if you get any on the paintwork.
David
Hi,
Having done this twice during the ownership of #2J50041DN I would not even try it with the chromed channel in place.
Yes, you easily get the “waves” in the rubber, it does not look nice and does not seal well.
You need to stretch the rubber a bit when installing, but not too much, or it will pull back once it gets warm in sunshine (ask me how I know).
Also once you have gotten used to how you get those pieces out, it’s not a big deal and you can clean and rust proof the very vunerable surfaces of the rear wing and window edge from the inside while you’re there.
And make sure at the same time no screw or pop rivet has gotten dropped into the drain of the coupé rear window bottom / drain area next to the sill (also ask me how I know it can happen) and block the drain. 
It takes a while to get them to fit perfect, but it’s very rewarding too, brand new seals also typically slow down the rear side window going up and down, make sure you don’t overlap them in the rear corner or the window mechanism will struggle (and possibly fail) in getting the side window all the way up or down.
Cheers!
Looking into the abyss, there appears to be a screw securing the chrome channel. Presumably there is at least one more. Is removing the interior trim panel the way to access these?
Hi,
Yes, I would not try to do it without first removing the rear seat bottom part (easy) and then open the rear quarter trim panel, you don’t have to take it out all the way, but form the rear so you get access to the screws, i think there are three or four, one was very close to the rear corner IIRC.
Cheers!
Ps. I might have photos somewhere, but I am traveling right now.