I believe you have a few options. I have sold a number of bottles at McTears. McTears are a Auctioneers in Glasgow, selling everything from kitchen sinks, fine art and antiques. Four times a year, they have specialist whisky sale.
Martin Green is the man to speak to at McTears. They charge 15% of the sale price, ut the prices they achieve are excellent, especially for top of the range bottles. On ebay, after ebay costs and paypal costs, it often comes to 10%, so I think its worth the investment.
Unless you have decent ebay rating, people will be hesitant in paying you top end prices.
The otheroption is whiskyauction.com. Mainly the mainland European market buy from him.
Make sure get at least £1200 for the Bowmore, if not more. Ardbeg 30, is worth £250-£275. If you want an indepent view on anything else, please drop me a note or post a reply on the website.