Your web site is now in my "bookmark" list of favorite places to visit in the future. Layout and navigation are well done, especially if you consider this a "first pass" for beta test. Never the less, I do have a few minor suggestions which you may take...or leave.
1 - "Contact Us" - The page is nice, but I'd expect to see most of the information regarding your personal involvement, background and rationale for this business to be included in the opening page "About Us". Normally I'd only go to the "Contact Us" page to ask a question. And I'd expect to find only contact information, perhaps with a pop-up email form to fill out and send. Instead I learned more important information about you and your business...which is good, just not where I expected to find it.
2 - "Gun Condition Report" This should be a very useful service. I trust you'll get a good deal of interest from those of us outside the U.K., especially from the U.S. Because the form is a print out and fax, I would add some basic business info to the PDF file: International Exchange Prefix with the Fax Number; Voice Number; and Contact Representative's Name, etc.
3 - "Shooting Breaks & English Tuition". Another interesting idea in your business plan. I suspect your American clients could make excellent use of the "English Language Tuition" portion, since most of us can not speak english...the King's version or any other kind...we just don't know it.
4 - When you hold an inventory of interesting firearms or have access to some that can be pictured on the site, I'll be a frequent visitor.
All in all an excellent start to what I believe will be a fruitful venture. The more pictures and color you can add, the better. Good luck.