Servus Dajehle,

just joined in because of you

You are right! It's the Gardeners World, September 2005 edition. As luck would have it, I took along the magazine in question with me, on my trip through Southengland in 2005. Recently I digged it out again, and stuck on page 63, with the wonderful orange blossoms. The accompanying text refers to "Thompson & Morgan" Online Seed and Plant Catalogues to order Clementine, but also says, that supplies are limited. But this you have already noticed

I am still browsing the internet for Clementine, because I could not find a supplier so far, who delivers grown plants to Austria. But if you live within the U.K., and are willing to reopen the chase, T&M could become your true clementine-heroes one day...

Good night, good luck and green greetings from Vienna!