2 downsides to that, it rather limits the choice, and it doesn't necessarily mean you get a top job done, it just lowers the chance it will be a botch job.To answer the last part Ben, Visit the manufacturers website for an approved installer, should get you someone reasonable, at best someone that knows the product.
My ex knows a really good installer apparently. Rather dashing looking chap too. And very intelligent. Not to mention charming.
And despite all that, very modest.
Amazing isn't it?