Yesterday I’ve searched for the Marmite chips, but haven’t found them. But I can get the Walkers products here, so I bought these:
I will try them in the next days and will report which one of them has to go to Room 101… 
I can get more different flavors, so I still hope to find the Marmite ones.
But a colleague of mine has found the termites extract:
I’m not sure if I should buy one glass, because the smaller ones are still too “large” just to try the stuff. 
(One of the smallest glasses costs 4 Euros in that particular shop.)
Side note: They are selling here British flour and baking powder… @tasse-tee: What’s the difference to German flour and baking powder?