Michael, what no one has told you is that there are two types of rear lamp cover!
Although essentially the same they attach to the body in different ways. Later cars (1978 model year shell onwards) had the kind that you see in FI Spyder's picture. Earlier cars had no vertical flap at the top, just a horizontal flap with a couple of self tappers in it - that sounds like the covers you have, wrong ones for your car.
The parts books (& hence Rimmers website illustrations) are a bit confusing here. The early lamp covers are XKC1550 & 1551, the later are XKC2647/2648, but the illustration shows the early type with the later part number. The actual photos on Rimmers website appear to show the early type trim with the later part number as well.
You have a later car - why? Because you have the 4 holes in the boot bulkhead for the vertical trim mat, also only found on 78 model year shells & later. Your bulkhead trim should have the matching holes which again are fastened with plastic studs - if not it's easy enough to make holes in the correct places. AFAIK earlier cars did not have a bulkhead trim at all.
Finally, the bulkhead trim is different between the coupe & the convertible cars, so make sure you get the appropriate one for your car.
Tony
<font size="1">1981 TR7 FHC Cavalry Blue
1980 TR7V8 DHC Jaguar Regency Red - sadly sold!
1977 TR8 FHC EFI Factory development car Inca Yellow</font id="size1">