harfields uk
http://www.harfields.com/Rare.aspx is trading with second hand boxes
for some range of manufacturers there is also
http://www.bat-hor.com/ from Netherlands
but for cheap figures, you will need some luck, check here at the marketplace regularly and e-bay and similar sites
considering the shipment costs, it is always questionable is it cheap in the end
great and not expensive web shop is
http://www.modelhobbies.co.uk/shop/cheers