If you do need to remove the Quarter Lights give yourself a bit of time. There is only two ways of removing them unless you are very lucky and none of the bolts, washers or the spacer are rusted to the Quarter Light lower hinge shaft. If you are lucky all you will need to do is remove the upper hinge. The two screws holding this can be accessed by removing the Rubber Seal that runs over the top of the Window Frame . Then remove the nut on the lower shaft. To get at this nut you will need to remove the Door Panel ( Door Card ), Speaker and possibly the Window Winder mechanism or Electric Window Motor etc. When lower nut removed the Quarter Light can me removed by lifting up. There is a spring and a couple of washers that will come off after you have removed the nut. As the Quarter Light comes out there is a spacer and washer between the bracket that is bolted to the bottom of the frame. More likely is the spacer is seized to the shaft. There are two ways to get at it as it will be VERY difficult to loosen if you try without doing one of the below. One way is to remove the Window frame complete. This is done by removing the screw that can be found just below and in front of the Window Frame. The screw is on the Door. When screw removed you can lift the cover enough to get at the two bolts holding the front of the Window Frame. Then remove the two bolts either side of the bracket below the Quarter Light frame. Then remove the two bolts at the bottom of the frame either side of the main window. The frame will then come out although there may be some sealer and or years of stuff holding it.
When removed you will see this.
You will now be able to get at the bottom of the Quarter Light assembly.
The other way to get at the Quarter Light spacer is to get a sharp knife and cut the rubber seal between the bottom of the Window Frame below where the Quarter Light is and the top of the Door. This is done from the inside. You will now be able to see the Spacer and deal with accordingly. Unless you need to remove the Window Frame for other reasons I recommend that you cut the rubber to gain access. Not a problem as the rubber can be refitted with some sealer/adhesive like Sikaflex.
The pictures below were taken from Window Frames removed from an SE5a (1974) that I purchased for the Engine and Gearbox. To remove the Quarter Light Glass is shown as to try and take pictures with the Frames fitted to the doors would be difficult. Hopefully the pictures will help as to remove the nut, spring and spacers will mean you will be working "blind".
Remove the Nut at the base of the spring and you should have these bits.
Remove Two Screws at the Top Hinge, you will have to remove the Rubber Seal. If your Seal is in OK condition it will have to be "peeled" back from the leading edge so as not to damage it. The seal on the frames above was no good so all I did was to dig a bit out to show the two screws.
Once the Top Hinge removed the Quarter Light Glass can be lifted upwards and removed.
NOTE. The bracket does not have to be removed, best if it can stay fitted as the two nuts holding it on will almost definitely be rusted ( see picture above ) and will cause great difficulty when removing, I removed it so as to show. One problem you may have is the Spacer that is closest to the bottom Hinge threaded part in the picture above does not have a round hole but has "flats" that engage in the shaft. A squirt of "PlusGas" and gently wiggling the Glass while lifting should loosen it for removal. Take care as the rubber seal is rarer than £9 notes.
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One thing that may be of help/use. The side windows ( Not the ones in the Doors but the long Ones ) are able to be swapped from one side to the other. The reason for this information is the chrome finish may have tarnished but by swapping them over the tarnished side will now be on the inside of the Car ( and covered by the Rubber Seal ) and what was the inside will now be on the Outside and so be nice and shinny.