the best place to sell a stamp from one country is to sell it to someone in that country.
I agree although this is not always possible.
The best way to sell is in the country's currency.
So you would do better putting the QV in sterling, the Canada in CAD and so on.
Only if you are signing on to eBay dot UK or eBay dot CA or dot AU or some such. Then you will appear in the local listings (not worldwide) and it would be more ideal then to list in that country's currency.
Some do this on eBay but the vast majority just list in their own currency.
I am OK with this as I have always had to exchange my Canadian dollar to US to buy stamps that I wanted so it is just part of the transaction for me.
Some are not so comfortable with exchanging their money for many reasons and so you must list in the currency of the marketplace, or the most people in the market so as to help to seem to be a good choice to buy from.
I have heard Canadians say well I am listing in Canadian dollars because I am Canadian etc etc and I wish them luck but the money and market (the vast majority of it here) is the US where they don't use the Canadian dollar. Strange but true.
You go where the people are, to sell.