There's a brief description of the company and examples of some of their sets on the UK Vintage Radio Repair and Restoration site.
The A. C. Cossor company was founded in 1908 - notes on the history of Cossor here.
Here's an example of a late Cossor set. An interesting example of an early UK VHF/FM receiver that tries to make the most of the much improved fidelity of these broadcasts. It features a well designed twin driver loud speaker, and "magic eye" tuning.
Details of valves for this and other sets can be found here.
Update - June 2009. I've got around to having a proper look at this set. It was in untouched original condition with what appears to be a completely original set of Cossor valves. Fed with a signal into the "gram" socket the output stage was good. The dial lamps were dead and the magic eye so dim as to be useless. The indication was of a set that had been treated well and used for very many years. Testing the valves on an AVO valve tester showed that although they were working emission and gm were low for all of them. Replacing the VHF double triode and the mixer gave clear reception on all bands - but only with the volume control at max. As the output stage was good - perhaps this valve had been changed (or the set never played loud) - I suspect the triode in the detector valve is weak. I also replaced the wax and small electrolytics, though only one tested very bad (you really have to remove these to test, so putting them back makes little sense as new ones are sure to give less trouble in future).
524 Melody Maker http://www.dsearleuk.force9.co.uk/Radio/Cossor%20Melody%20Maker%20524.htm http://www.vintage-radio.net/forum/showthread.php?p=216538
549 Melody Maker