I think your best option would be to sell via auction, I am sure these two expressions would attract a lot of interest. There are the two large auction houses in both Glasgow, which is McTear's http://www.mctears.co.uk/
, contact Stephen McGinty; and in Edinburgh, Bonhams http://www.bonhams.com/auctions/
, contact Martin Green. There is also a new auction house, or I should say new to whisky auctions, Mulberry Bank, also based in Glasgow http://www.mulberrybankauctions.com/home.aspx
, contact Angus MacRaild, although new this auction house is attracting a lot of attention. Another possibility is to sell via an internet auction site; if you wish to go down this route then the best site in my opinion is Scotch Whisky Auctions, also based in Glasgow http://www.scotchwhiskyauctions.com/
contact Tam Gardiner or Bill Mackintosh, very helpful people.
I think it would be worth getting two or more valuations and please look carefully at the small print as they all have different commission rates plus extra charges for Photographs, handling and reserve pricing. Whatever you do, do not sell via eBay.
The estimate that I gave was at the lower end, under the right conditions there is the potential of realising a much higher premium.