Paul,
Others have correctly directed you on the location of the seam in the seal. As to the boot light, I installed courtesy lamps in the footwells of the interior. Amateur installation when compared to Roger's. However, what I did that is a little different than others, is that I used a modern key fob that has button switches to control my lamps in the interior and the boot, I can either push a button on the fob and just have them come on for forty seconds and then that fade out, or I can switch them on and they stay on until I turn them off. It is a nice feature that can be used when you are approaching the car to enter. When I did this, I had committed to myself that I would not drill any "new" holes in the car, so that if I ever wanted to drop all of my modifications and go "original," it would be an easy transformation. As it turned out, I wasn't 100% pure, but I made the effort. Looking back on it now, door jamb switches would have been fine. Oh well!
At one point, I also considered using a mercury switch operated lamp that was going to be mounted in the boot lid, so that when you opened the lid, the mercury moved in its tube (like a thermometer) and switched on a pair of lights. I ultimately rejected that approach because I felt the lamps were too far away from the boot and just didn't provide enough light.
Since the lamp in the boot is visible, I decided to use a license plate lamp and just took off the chrome surround, because it blocked out the dispersion of the light. It all looks "period" correct even though as stated by others the Healeys never put a lamp in the boot. This modification has turned out to actually be useful as I have had several occasions when I needed to root around in the boot when it was pitch black outside.
Lin