Buster Puzzle Books - incomplete listing, can you help?

Spotted this on ebay the other day and I thought I'd see if I could scoop up images of the cover of the 'Buster puzzle book' as they were a series I'd not come across before. Here's what I've found so far...The series ran from 1975 to 1984...

Buster puzzle book 1975 (25p)

Buster puzzle book 1976 (??p) 
no image to hand


Buster puzzle book 1977 (30p)

Buster puzzle book 1978 (35p)

Buster puzzle book 1979 (40p)

Buster puzzle book 1980 (??p)
no image to hand

Buster puzzle book 1981 (??p)
no image to hand

Buster puzzle book 1982 (50p)

Buster puzzle book 1983 (50p)

Buster puzzle book 1984 (55p) 

Buster puzzle book 1985 (60p) - on the right