I'd probably drop anything below 9x6, if you're selling your photos as art then IMO 6x4, 7x5 are too small, personally I wouldn't hang anything less than a 9x6.
I don't think I'd offer digital downloads either, for example I could canvas print a digital download for £26 + your £10 opposed from the £200 on your site.
I don't like this sentence;
As a professional photographer my work mainly consists of equestrian, people, pets and areas of interest in and around Stoke on Trent and Staffordshire.
I would suggest;
I'm a professional photographer, with work covering ....
I'm a professional photographer, current projects include .... I'm available for ....
I'd probably make more of a feature of project stoke, news paper coverage ect. you need more than one photo in the equestrian folder.
Layout and colours are good and the template is pretty slick.
Good luck with the site!