DG - OK, had a look at your listings and TBH I don't think there's much you could improve, just a few tweaks - it's probably just that clothes aren't selling at the moment compared to toys and gifts etc. But here's my tuppence worth anyway:
Children's books - I've never managed to sell used books when listed individually unless it's a huge encyclopedia or annual - have you considered doing a bundle of the Kipper books and starting with a higher price? Also, I think as they are used you need a picture of the actual book rather than a stock photo, and give a little more detail on the condition by pointing out for example that there are no scribbles on it or ripped pages etc. And check your P&P cost for the individual books - if they are slim enough they could probably go as a 1st or 2nd class large letter and you can bring that down.
Clothes - fill in ALL of the item specific details - colours, material, brand, length etc as this is what people use to search. The 2 piece dress and jacket I think needs a photo of both items plus 1 of them together.
And the only other thing I'd say is that your stating prices are a bit too high, but you knew I was going to say that though I understand why you don't want things to go for 99p - maybe you could bundle some in the same size or accept that they either won't sell or not until after Christmas.
I've taken a while to accept that if something only sells for 99p after weeks of re-listing then that's all it's worth (on ebay anyway), and the competition on clothing is high.
Hope that's helpful x