While Dorset Police do not currently auction their seized goods online they do hold in-real-life auctions quite regularly. Both Cottees and Davey & Davey handle Police Auctions for the Dorset area. Check their websites or contact them directly for more information.
Cottees
The Market, East Street, Wareham, Dorset BH20 4NR
http://www.cottees.co.uk
Davey & Davey
Poole Salerooms, 13 St Peters Road, Parkstone, Poole, Dorset BH14 ONZ
http://www.daveyanddavey.com
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Dorset Police don't seem to have any live auctions just now.