Time of year probably is biggest drawback, wait till spring if you can afford it. I think air-cooled Dukes old and new are a bit of a drag on the market generally; I only got £2600 for 'T' 900ss in pretty good nick last September.
If you want a free advertising outlet try
http://www.adtrader.co.uk/ Can't say much about their effectiveness but they have a high paper circulation plus the website.
I read somewhere that good SS/SL/FE's are beginning to hold their value in the States, though they are notoriously obsessed with 'investment value' of their bikes.