The only one I know about is P and L Mini's in Thurnscoe in Barnsley.
They have been a classic Mini specialist for years and have been working on the new car since it was launched.
As the post says above it might depend on what work you want if they can help or not, they are certainly worth a try.
Their web site is www.plmini.com
and the new Mini has it's own section, contact details etc.
Hope this helps. I don't know of any other specialists.