I disagree about the comment about the size of the font but would agree that Arial or some other font would look better than the times new roman you have. I disagree about the font size only because of the demographics of wealthier pet owners (who can afford your product) , the majority of which are older and generally prefer the larger and easier to read type.
I also disagree with the need to get rid of the horizontal scrolling. I think you do a good job of using the extra screen real estate to engage your potential client(s).
Your alt text references could be better utilized. Try changing the mouse over, and alt image text tags to something that will get you more
SEO mileage. For example on the "Dog Gallery" mouse over, you should have "Pet Portraits - Dogs" for example. Work in the words pet portraits everywhere you can using the image alt tags.
Delete these tags in your keywords, they are diluting your ranking. (pet gifts, dog pencil drawings, portrait, portraits, watercolour, UK, England, Pauline Gledhill, pet artist, canine art, dog art, pet). Leave all your keywords the same as they are now except for that.
You are shooting yourself in the foot when you include "non keyword text" within your h1 tags. Here is what you have ( <H1><font face="Papyrus" size="+3">
Pet portraits beautifully portrayed in watercolour or pencil taken from your favourite photograph.</font></H1> )
You should H1 tag only the keywords you are using that are present in your text. In this case (the example above), you should only tag <h1>Pet portraits</h1> for example. (this example is oversimplified give the bold and strong tags that you used, but I hope you get the idea.)
You need to get a dmoz.org listing and some other directory links wouldn't hurt.
go re-submit your url to google, msn, yahoo, dmoz, and some other directories.