Hi, Jo...
I would have to stick with the $400 (or higher) selling price or trade value, since the last two £10000 plaques from Sporting Club that I sold were $400 each... The 3-pc. set that was on Spragg's list came from a collector whom I sold the set to for $1,800, because the last two £1000 plaques sold for $1,000 each.

Condition and series variations can also determine price.

I have not noticed where duty, tax or shipping or buyer's premium would affect the price of any item on eBay, Potter & Potter or any other auction house, anywhere.