UPDATED: 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 at least 1985...

Now added in the 1976 special (thanks to Cristiano Pereira) - so that just leaves 1980 and 1986+ to find 

Buster puzzle book 1975 (25p)

Buster puzzle book 1976 (25p) 



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 (45p)

image c/o Comics UK website

Buster puzzle book 1982 (50p)

Buster puzzle book 1983 (50p)

Buster puzzle book 1984 (55p) 

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