sadly I often get rung up by relatives of deceased model engineers, some of whom have seen inflated prices for single issues on eBay and think they have discovered a treasure trove, others just want them to find a good home at a modest price.
Sadly, there isn't as much demand for issues beyond about 20-25 years ago as you may think – many people seeking back issues want to complete a relatively modern project, although there are exceptions.
Don't assume volumes will sell for many times the price of the individual issues, or that 74 volumes will sell for 74 times as much as one volume.
Some periods are less popular than others with buyers, so prices vary greatly.
Selling individual issues will drive you bonkers, and be realistic about postage costs – paper is heavy in bulk.
Most people want a run of issues that cover a particular build, typically one or two volumes, maybe more.
You can advertise these on our classified ads on here for free, but it may take years to sell them all.
A few people may be willing to buy the lot, but expect far less per volume if sold this way and potentially a long wait to find a buyer.
If dealer is willing to take the lot, this might give you the best return if you are unwilling to wait the time it would require to sell all individual volumes, and possibly quicker than waiting to find a buyer for the lot at not much more. A dealer will have the space to store the volumes waiting for a buyer and may be able to complete incomplete sets or replace damaged issues.
Since the Toolbox in Devon closed down, I'm only aware of Bookland on the Fosse (related to Tee publishing) specialising in old volumes of ME/MEW. It would be useful to know of any others, as I doubt Bookland wish to buy all the sets I point in their direction.
Neil