for comfort - it's pretty difficult to read at that size.
You should place a copyright claim at the bottom of the pages - or at least at the bottom of the homepage.
Why have you put the site-map into a pop-up? It's irritating, and there's no 'back' button on the site_map.html page - you're left marooned there.
A few more images would be good - they always add interest to sites that have plenty of text.
To my mind there's not much point in having an index page with nothing on it - far better to amalgamate the index and welcome pages into one. Whenever I land on an empty index page I feel like paying the designer back, and simply clicking away again. Your homepage is your shop window, so why not use it as such, and showcase the business?
It's really important to check and double-check site text for typos; nothing lets a well-written page down more than careless errors. Take a look at your tariff page and you'll find this, for instance:
"Please not that some work....."