Funny that. I don't actually remember any adverts but I was an avid UK Marvel collector from the early 70s. Started off with MWOM, graduated to Spider-Man Comics Weekly (and can distinctly remember running around with issue one's free mask (er, paper bag) on) and then jumped about to all of them - The Avengers, The Titans (when they went all funny and put them in a landscape format), The Superheroes (remember getting told off for staying out and hanging around the newsagents late on a Friday night when they got the next days stuff out to get #1!).
Getting those comics each Saturday morning and sitting outside in the garden, swapping and drawing our own versions are probably some of my most cherished kids memories.