When I was using micro four thirds cameras, I was very successful at selling on our sister site
Mu43. It helped a great deal, of course, that I was
very involved on that site and was a "known" entity...as far as I could be known by people who hadn't met me in real life. My point, however, was that because I'd been so involved I believe that my being known worked very much in my favor. I also always priced my items at extremely fair prices. My goal was to sell and not to make money. Very few people are going to by used what they can by new for a few hundred dollars more. In addition, I sold to people in Australia, Spain, New Zealand, Canada and the USA. I don't think I ever sold anything to anyone in the UK. Not sure.
Many people find the site Fred Miranda to be a good place to sell... It's also a good place to check prices. eBay seems to be a good place for many and for local sales Craigslist seems to be good - especially because you can meet, and exchange your camera, etc., for cash.
I hope more people will add their tips. I know that I have been helped in the past by others who are known sellers and I've appreciated their help very much.