Ebay is a very good marketplace but you need to put in a bit of work to get the best from it - how to structure the selling process and monitor its progress - so it depends how much time & attention you could give it.
The first requirement is being able to give a full, accurate description - make, model, work capacity, voltage, etc etc. Good photos help a lot. But people will travel a hundred or two miles for something they want. The second consideration is deciding how you'll accept being paid and being alert to possible scammers. Offering pallet delivery for heavier items (via Palletline et al) is another option - but you'd have to palletise the items, strap and wrap them in advance.
Gumtree has a more local focus and is probably easier to manage (fewer protocols). But as above, it involves people coming to your home to inspect / buy, so you have to be comfortable with that. I'm not a scaremonger - most people are honest & genuine - but you at least have to be alert.
You could consider a job lot, by the way, so that it all goes in one hit, but this constricts the market a bit.
To make life easier, there will be auctioneers hopefully not too far away that would remove it all and incorporate it into one of their periodic auctions that include that sort of material. That would remove you from the stress and time input of handling it all yourselves. Ask around.
If I lived nearer I'd help out with descriptions / photos etc, but you're a bit far ...