I recently bought "The Ultimate Hammer Collection" (21 films) and they all look fine. Not great, but fine. All Optimum. Also got the above mentioned Optimum 2 in 1 Vampire Lovers/Lust for a Vampire and thats great.
Twins of Evil, one of my fave Hammers is also available from 'Network' and I picked that up recently as well. Lovely film.