Many circulation coins, such as commemorative £2 do not sell for much above their face value, if they even sell at all. Most people want Proof or Brilliant Uncirculated coins. If there is a whole set of coins e.g. all £2 set this could sell if it is at the right price and in the right condition.
Single Proofs or BU's
Single proofs and BU's normally sell as longs as it is priced competitively. Have a look first coin catalogue and at other ebay auctions for the right price. If you know this, buy it now is often the best way of selling. Checking the price of the precious metal, if any is also helpful, never go below this. This is called the melt value (although melting coins is illegal.)
These are the most expensive and sought after item. People will pay extra for it being in the original container and will also pay depending on quality. People find that proof sets are the most desirable. However, some sets that come out every year can be very hard to sell, such as the Royal Mint (year) Coin set.
These are very good for lots of common all one type of coins. Son't worry about the individual quality of the coins but the average quality and the quantity. Sometimes this is the best way of selling very common coins, such as the victoria bun.