Hi Alan,
Your site/theme looks really good so dont get changing the design at all, just needs a little snagging. He's done you a nice site!
You need to get your designer to save your images optimised for web. Essentialluly the file sizes are too large.. your asking your visitors to download really large images which is unnecessary. In photoshop you can "save as web" and reduce the quality and size down. This will sort alot of your slowness out. 8 seconds to load a page will make most people click off before it's loaded.
Should only take him 2-3 hours to resave the images. It's a really simple job just boring (if they all need sorting that is). For example on your home page you have this image (double click and see how massive it is.. the shells the whole width of my screen) Broken Link Removed You could even do it!! Just need to download photoshop demo and a bit of instruction.
You have also got a link in the code thats causing issues. (wont really give you much in terms of speed when fixed but it should be fixed nevertheless)
The link is
link rel="stylesheet" href="[DLMURL]http://johnclarkenaturalstonework.co.uk/wp-content/themes/smallbiz/css/smallbiz-options.css.php[/DLMURL]" type="text/css" media="screen"
It's got two file extensions on the end of the link.css & .php so just delete the .php off the end and all will be sorted.
I would also get him to remove a plugin called "Stats for wordpress" as you have lots of plugins installed and you can just embed Google Anylitics and Google Webmaster Tools which are both free. Which renders this additional plugin useless.
Apart from that it looks good