Teak Decks - Maintenance

My teak decks look as though they have been well cared for by the previous owner (I bought my Beneteau last October), but during the winter the decks have been going green in places with mildew. Having looked on the internet and in particular other owners associations, Hallberg and Najad owners swear by a product called Boracol and say it keeps the decks clean for up to a year. They also say it can be purchased from chemists or hardware stores but I can't find any that stock it. Does anyone know where to get this from or have experience of it please, I can't find a stockist via Google. I sail on the east coast (Essex) and work in London so any stockist in that area. Alternatively does anyone have any advice for maintaining teak decks.
Paul