I am a freelance embedded developer/consultant providing services through my company, Antronics Ltd:
Antronics Ltd provides consultancy and embedded firmware development services on a contract basis, with particular experience in GSM & M2M applications:
http://www.antronics.co.uk/services.htm
Clients have ranged from big-names like BT to small, local start-ups:
http://www.antronics.co.uk/portfolio
Key competence is interfacing, control, and communication with embedded microcontrollers.
We may also be able to assist with relatively "low-level" PC software - especially involving serial communications - such as is often required during the development & testing of embedded devices; For an example, see: http://www.antronics.co.uk/downloads/comled.htm