I looked at a few of your items, they are overpriced. 

Used tennis ball, used shuttlecock  radiator key.

I can get all these items new for much cheaper.

To add to @tobiasd4  correct advice,  be aware buyers have a Best Match option to find the cheapest item if there's more than one seller selling that item,   and there always is.

Check out your competitors,  even selling those items for 50p less,  may attract your buyers.

You do need to lower your prices.

@nonipaagee 

I have to agree that your items are overpriced - don't forget that buyers are paying for the postage as well as the item price.

For example, you have a very obviously used hose connector up for £7.95 plus £2.26 postage, and on your page sponsored sellers are offering a new one for £2.56 with free postage. A new branded Hozelock one is showing as £2.85 free postage, so there is no reason why a buyer may be interested in yours.

I'd take some time to check what other sellers have listed similar items for, and the price they've sold for.