The best researched source of information on this sort of question is still British Planemakers from 1700, third edition.
Over six pages, it describes Moseley as the pre-eminent London planemaker of the 19th century. It also attempts to sort out the marks most likely to have been used in different periods of the firm's history.
For the name MOSELEY on its own, it suggests the period 1809-1818, before it became Moseley & Son.
It's a long, complicated story with the firm trading from various addresses as wholesalers and retailers, but it does confirm an early date for your plane.
It's also worth mentioning that in 1892 the business and trademark of John Moseley & Son was bought up by Marples who moved plane production from London to Sheffield by 1904. Until at least 1938 they offered their range of wooden planes with the purchaser's choice of branding - you could choose Marples or Moseley.
This may sound odd, but there are plenty of current examples particularly in the car and white goods markets where the same model is branded differently in different markets.
The effect is that planes marked Moseley & Son are much more common than your early style.