I'd use a UK based SEO secialist but really there is no difference between carrying out SEO for a UK based company and carrying it out for a US based company - apart from the cultural issues and spellings (optimise / optomize for example or trousers / pants).
There is not such thing as UK based company. If you need SEO to be done for the company then you gotta professionals thats all.
For very best SEARCH ENGINE OPTIMISATION outcomes I suggest using Google Search Bot: http://is.gd/gsbsoftware Using that application I have placed my web page to first page of Google on a quite high aggressive search term.
use geo mate tags
How to seo for a uk based company
