Hi Rhys,
Taking a look at your site, your links all seemed natural and within reason. ( I did think the homepage was a little light on content - mostly just navigation and quick links to products. But that's another conversation.
"Best practice" is to consolidate your non-important links into a format that makes sense and is human friendly. Rand wrote a post about footer links awhile ago that still works today:
http://www.seomoz.org/blog/footer-link-optimization-for-search-engines-user-experience
I wrote about this in another Q&A thread a short time back.
Today, you don't hear much about PageRank sculpting. Most SEOs don't bother with it, partly because of it's decreased effectiveness, but also in part because there are more effective ways of controlling the influence of links.
...Link "equity" or PageRank, (or MozRank), is only one small factor in the overall value of a link. Anchor text, position on the page, and a host of other factors all influence how much influence any given link can wield. Here's a good introduction on the subject (again from Rand)
If you "no-follow" your important contact pages (about us, etc) Google may have trouble finding and crawling those pages. Because these are both valuable pieces of content and trust signals for your site, this probably isn't the outcome you want.
To summarize: Adding nofollow in your case doesn't make sense. It really only makes sense in a very few cases, and isn't as effective in controlling ranking signals as many people would like to believe.
Hope this helps. Best of luck with your SEO!