Builder for Home office/garden storage

Can anyone recommend someone for the following.
Want to put in a custom built 2 room structure in back garden for home working and storage - approx 25 sqm. I don`t want to go down the log cabin path, rather have something that uses the same materials as the main house.
Also approx cost?
Thanks

how about something high spec like this??

http://www.shomera.com/