Heron Plastics Ltd ad, Autosport 1962
Not a name I was familiar with, found when leafing through some old copies of Autosport. The Europa actually gets a Wikipedia entry and there's a good page on it here: www.anglia-models.co.uk/specials-heron.htm
I can't find anything on the Rejo.
I'm not sure if their works was anything very much! Calvert Street is just off the A206. Based on the house numbers, there seems to be a yard and what might once have been a workshop behind the houses here: maps.google.co.uk/maps?q=Calvert+Road,+London,+Greenwich&...
Bing doesn't show much more, if it was the mews building in question then it now looks to have been converted to residential. Interestingly, one of the views on Bing shows a massive great building (hospital?) which on everything else just shows up as a vacant site.