In that case you've got them mixed up - because the Mk2 had a double skin boot;
Part no:
28G110 BOOT LID ASSY., single skin type 1 1959-67; Austin and Morris MkI. Cooper models 1961-66
8G9270 BOOT LID ASSY., double skin type 1 1967-69; Austin and Morris MkII. Cooper models 1966-69
Mk1 look like this;
And with the cardboard liner removed - you can see the singel skin and "frame":
The Mk2 lid on the other hand - look like this:
I assume the 5,8 kg is for the Mk1 lid without the liner..
Tell you what, do your own list!