Think about what you want from your hens. Hybrids can be docile, will lay very well in their first couple of years and be good for a beginner. They are also generally cheaper to buy.
Pure bred hens will lay less but over a longer period of years and will generally live longer. They will cost more too.
I started off with a couple of rhode rock type hybrids who are now about 2 and their laying is starting to decrease now and I am hoping to get 1/2 pure breds in the spring.
If eggs aren't so important to you then you may be looking for a more ornamental type of pure breed.
Also think about the environment you will be keeping them in. Some birds are more capable flyers than others which may be a problem if you have a garden with low fences. Some breeds are easier to handle than others, some are generally noisier than others.
I would have a look at the breeds that are available at poultry sellers within your area and then do a bit of research online. As mwntioned above there is a list of poultry suppliers on this website. I also found 1 near to Usk earlier today when I was looking for suppliers in south Wales (I am from Cardiff) , which may be useful:
. http://www.cosyhens.co.uk/. I haven't checked them out yet but they aren't too far from Newport so may be worth a shot.
Hope this is of help. Whatever you choose I am sure you won't regret it, have fun!