ROTJ Weekly Issues from 120 onwards seem to be the most difficult to find, probably because they were being produced in fewer numbers and less people collected them. The later issues of ESB Monthly are toughies also. I couldn't put a figure on the issues with free Ewok stickers – it would be worth giving them a run on an auction site.
I'm envious if you have a chance at grabbing a near complete collection, especially if it runs to the end of ROTJ Weekly.
Incidentally I have hundreds of spare Star Wars U.K comics, from good condition to very poor if anyone needs issues to fill gaps in their collection. I would be willing to sell them fairly cheaply, or trade for issues that I need to complete a mint set. Most of my ROTJ Weeklies are the ones from my youth, so many of them are in dire need of replacement.
Craig.