Founded in 1995 with a HQ in Belgium, Stagg is a major European importer and distributor of musical instruments. They do pretty much everything, Guitars, Banjos, Woodwind, Percussion, Brass, Cases, everything! Including a fairly full range of Ukuleles in all scales, going from Budget to Semi-Serious (but not, it appears, Banjoleles super scales or any string options). The better models are made by Hora and re-branded with the rest coming from China including some budget type Sopranos with colourful graphics.
I have seen Stagg instruments on sale in the USA, Thailand and Australia as well as Europe and they claim to do worldwide distribution.
Eastcoast is the "house" brand for the PMT (Professional Music Technology) chain of UK music stores
Rocket is the house brand for Normans Musical Instruments, another chain of UK music stores.
Ridgewood is another redistributor in a similar vein, but I don't know who is behind this rebranding?
They all have a large online reselling presence and use their brand names on instruments they acquired from Stagg. From the website(s) it appears they often miss out their rebrand and sell with the Stagg logo still on(?) but there are some Ukuleles around with their own logos on the headstock or in the sound hole instead.