Some of your t-shirts don't have sizes at all. I would not buy without knowing what size it is. Even the ones that have sizes like Small, Medium,etc should have a picture of a size chart giving the actual measurements for the main parts of the shirt for each size. Being in the US, I have no idea what the measurements are for the equivalent in UK sizes.
Your return policies are illegal for the UK and EU countries, so you have no Seller Protection and Etsy will not enforce them because there are laws that force you to give refunds in those countries unless it is customized or personalized. Since you don't take returns, your customers have up to a year and a day to ask for a refund, and they won't even have to return the merchandise.
Especially with clothing that might not fit, and is not personalized, I would not buy anything without a return policy, and many people will feel the same way.
Your descriptions don't have much useful information. I would want to know what the fabric is made from, and washing and care instructions. The type of printing is the only useful thing included. I would want to see a sizing chart. Put all your promotional general information that you are putting on all your products near the bottom, after all the specific information for that product.
Most of your tags are single words. They should be multiple word phrases and as specific to that particular product as possible. People who search with one word general phrases are just browsing and don't even know what they want to buy yet, or if they want to buy anything. Plus those terms are ultra competitive. When tags are very specific, people already know what they want to buy and are likely to but the first thing they find that meets their criteria, so when you do get a click, it is much more likely to result in a sale.
