Microtext Ltd.
From CPCWiki - THE Amstrad CPC encyclopedia!
Microtext were originally based at 7, Birdlip Close, Horndean, Hampshire but are now at 3 Rose Hill, Lovedean, Waterlooville, Hampshire.
For the CPC, they made the Teletext adaptor and the Teletext adaptor Tuner add-on.
They also made the market leading (at the time) adapter for Micro$oft Windows in the early 90s.
They still do manufacture a Windows Teletext decoder but, with the country going digital, this is now of limited usefulness (presumably).
They now provide computer maintenance and web design services - according to their web-site at: http://www.microtext.co.uk/
