The site looks great. The one thing I would recommend would be to make the images the actual size you need. Some of the images you like they are squeezed or stretched.
I noticed on some of the images that you changed the size without keeping the proportions of the picture the same. You can do that a little bit, but too much makes the image seem distorted. The one that sticks out to me is the man relaxing.
This image is 400px high like the space you want to fill, but slightly narrower at 700.
Well done Julian - for the site and being brave enough to post your first site here for feedback! I agree that coping with Fireworks as well as Joomla when you start can be demanding!
One query: was there a reason that you decided to make your site so wide? My 17" screen chops the right modules in half which feels a little odd as the pages are not that long. I suspect this will apply to quite a lot of people who haven't upgraded to 19"+ monitors yet.
For really old monitors to be safe about 800px, but I think most sites these days are around 950px wide. RT templates tend to be about 950 - 1000 px wide by default so I usually keep to that. Changing the width of your template may give you an issue with the images on the cars page - but you could always make the pics smaller and use RokZoom to enlarge them if needed.
Making it a bit smaller would also pull the site together and probably make it look a little more professional - but all these things are matters of experimentation until you find what works for you.
Another lesson learned Im not sure how I managed to get the site width at 1100 px think it was when playing with header and logo
Im Using the JCE Editor mambot in this site. Is there a way of knowing or setting the usable writing space so it fits the size of the available module size, or is this wet by the size of the module?