Environmental pond/lake help?
 

I've got a field approx. 10 acres in length that I used to keep horses but am now considering turning it into an environmental area to attract wildlife. I am considering digging out an area so that I can create a large pond/lake that will serve as an area to attract wetland animals and birds.

I live in South Wales Carmarthen and was wondering if anyone had any advice on what species of animals I should be realistic in tempting to the area and how I should go about this?