I'm a web-developer and not really a designer, so I can't comment with too much authority on the design, though here's my thoughts:
Firstly: Damm good effort, designing+implimenting a website from scratch isn't easy - don't let my comments take anything away from that.
I like the image display/navigation, however I'm with Justin on the single-template thing.
I'd also add that I'd like to be able to jump between the subjects/categories rather than having to go back to home each time (1 click >> 2).
Design wise on the front page, you've got margins at the top and sides, but the blue border touches the bottom of the window (in IE8) - it makes it look crowded. Personally I'd loose the border completely, but that's a preference thing.
Also, logo in top-left = good. But good practice is to make it a link back to home (it's standard, people expect it, people get fustrated when it doesn't do what they expect)
in the actual code:
your <meta name="keywords"> tag, you've got
Editorial Photography,
Photographer Buckingham, Commercial Photography Milton Keynes, Corporate Photography Milton Keynes
this would work better as
Photography, Photographer, Buckingham, Commercial Photography, Milton Keynes, Corporate Photography, Editorial Photography.
- this might just be SEO voodoo, but it ought to index better splitting the town off the 'corporate photography' and 'editorial photography' keywords.
also - add yourself a <meta name="description"> tag - this provides the text that'll appear under the link to your site in Google results - and it's (nearly) always better to specify than to have google generate some from your content.
Lemmie know if any of this helps - sorry if it's a bit critical :s
M