An eBay listing will get you the market price, and as long you:
- write the ad clearly and describe the bike accurately
- have copious sharp images
- set a realistic reverse price (or better still have no reserve at all)
- run it for a reasonable time (7 days typically)
- set it to finish when people are at home (Sunday evening, typically - and not on the Bank Holiday!)
- lastly, pop a link to the listing on here & other eBike forums so people easily find it
I sold 7 bikes last year in eBay in a garage clear out. I got good prices for all of them - and two got crazy prices.
I'd say the only two downsides are:
1. A % of the sale is taken by eBay as commission - 10% if I remember correctly
2. You will get requests to post the bike, rather than collect it. You have to decide upfront whether to offer this. I didn't because of the hassle (source a bike box, and courier + add that cost into the P&P calcs).