As yet I have been unable to find any comprehensive information about this company.
Most of the references to "Magneta" refer to another company of this name who produced a different style of master clock with reversing impulses generated by turning a coil operated by the master clock.
The Magneta Time Company was a division of the British Vacuum and Engineering Co Ltd. and it appears that the Magneta Time Co absorbed the Silent Electric Clock Co in the mid 1920's.
Silent Electric were a company founded in 1908 by George Bennett Bowell who had previously been in partnership with Hope Jones.
Bennett opted to use the hipp toggle principle and obtained many contracts with the Post Office for the supply of these systems.
Around 1925 the Post Office standardised a design based on the design Bowell had developed, (the PO type 36) and went on to invite tenders from other manufacturers such as Synchronome, Gillett and Johnston, English Clock Systems (Smiths) and Gents.
The name "Goblin" was also used by the Magneta Time Co as a trade name for some of their products including early synchronous clocks and the famous "Teasmade" device which boiled water, poured it into a teapot and then sounded an alarm.
The factory in Leatherhead was called the "Goblin works"