Please be advised that getting a used model railway buyer in, as Dunny notes, might give you the biggest disappointment in your life, as well as serve as an eye-opener. Last year I got one of the people who advertises in our press as the 'very best prices for your much-valued models!!!'
I was trying to move on a LOT of H0 stuff, a lot of it brass - all mint and boxed. As an example, just two of the numerous locos had cost me almost £1800, and the brass cabooses, at around £300 each, made their own pile, as did the thirty-something passenger cars. In all, there were over a hundred items of mint rolling stock and locomotives. I was expecting, having seen his retail prices, to have been offered around £3000 or so, and while I would have been downhearted, would have understood that he had to 'make a living, gov''.
I was gabberflasted at this offer of £600.
One of the locos like mine was sold on the usual online site for £1100 recently.