You're photos aren't bad, there are a few images that could be sellable. However there are simply too many, you've fallen into the trap that a lot of businesspeople end up going into, which is you've forgotten the customer. It's all well and good to put up a website and start trading. You'll get some sales just from people bumping into the website by chance, however you'll never reach large numbers like that. You need to draw people in and encourage them into making a purchase.
Firstly, work out what a good photograph is. By that I mean you need to look at good composition, use of light, points of view, ensuring that exposure is spot on, and capturing the right moment. Indeed some of your images are rather snapshotty and touristy, some though have potential. Cut the pseudoartistic crap and work on bread and butter shots first. You can discover your creativity later on.
Images like http://www.thomaszavros.co.uk/p770870201/h2dca28a1#h2dca28a1 and http://www.thomaszavros.co.uk/p146834430/h3f1ff35f#h3f1ff35f and http://www.thomaszavros.co.uk/p1060565789/hff89f5e#hff89f5e could be potential sales. They're relatively interesting and unobtrusive, photos that can go on someones wall.
People like choice, but right now you're giving them far too much of it. You need to make it easy for customers to make a decision, help them by directing them to a good choice. Cut down on the content, right now you have hundreds of mediocre images that nobody cares to look at, you should try to target a specific audience, so you'll need between 15 and 30 top quality images, which perhaps fall into 2-3 different themes.
Only offer them a top draw service for that, make prints at 8x10 or larger and limit the customers options to just a few key sizes (e.g. 8x10/12, 12x15/18, 16x20/24), this allows you to print a number of each photo and keep them as stock, which allows you to negotiate a better price for the printing services. I personally think you're selling at too low a price, you can sell unframed 8x10's at around £10, if you can produce top quality imagery. Additionally it's worth adding a framing service, again at extra cost, and likewise make sure it's gold standard, whether you choose to keep frames in stock or order them as and when you need is a decision to be made on assessment of trading.
Furthermore, by reducing your content in your website it will reduce your overheads for the site considerably, as well as that it may increase the speed at which it runs. I think right now partly due to the vast amount of content, and also due to the interface, I feel the website is messy and that further will drive potential customers away.
Bottom line is that selling prints is an high end retail industry. You cannot use the wal-mart model for this, you must identify and connect with your client and produce products that not only do your customers want, but products that make them feel special. I also think you are slightly too naive about running a business, you need to remember taking the photos is just the first part, getting the business right is how you pay the bills! Now I've already said far too much and should really be charging for business advice, though much of this really is just common sense.