There were at least two U.S. companies that had showrooms & sold inventory in London from the late 20's right up to WWII, Cambridge & Tiffin. Not sure about Heisey, but wouldn't suprise me since the other two were there. Tiffin's Gold line in Royal Blue was a hit in London during the 30's & sold very well. Cambridge flower frogs did decently well & so did their general line of opaques, Ivory, Primrose, Helio, Jade & Azurite.