Bubblyrat, is that true..A wok in...?

"It was just a nice ,jolly, lively, tune,with a rather evocative title !! How could it fail to seduce a sentimental nation like the British ?? You"ll never understand us, will you ? !!!!"
Apart from "never understanding british people" to which I do not agree to because I'm coming from Hamburg (known as most british feeling/minded town compared to total Germany)your statement seems to be reasonable.

Additionally, heavy rotation/playing by dj's on the radio could have been the rest of this successful story.

And last but not least, "Black Forest" by Horst was an instrumental, i.e. without any words. If he would have included some singing e.g. by himself I would doubt any success in the UK. Apart from Heinz (Just like Eddie)and some sidemen in groups I cannot remember any german artist who has had a smash hit in your country. Am I right?

Manfred