It's quite a puzzle. There was a sweet bar called Twix that was renamed Raider (pronounced rider) and then back to Twix. So when I wanted to buy one called Nuts I pronounced it noots, which met only ridicule. I went to a German course on Word for Windows, since when I have often muttered to myself Vörtt. Excel is pronounced on the first syllable.
Wells says the authors compare the German and English pronunciations of Buckingham Palace. I'm surprised they don't give 'ham' rather than 'gm' for the pronunciation.
A famous example of the difficulty of th for Germans was a Loriot sketch with Evelyn Hamann:
Auf dem Landsitz North Cothelstone Hall von Lord und Lady Hesketh-Fortescue befinden sich außer dem jüngsten Sohn Meredith auch die Cousinen Priscilla und Gwyneth Molesworth aus den benachbarten Ortschaften Middle Fritham und Nether Addlethorpe, ferner ein Onkel von Lady Hesketh-Fortescue, der 79jährige Jasper Fetherstone, dessen Besitz Thrumpton Castle zur Zeit an Lord Molesworth-Houghton, einem Vetter von Priscilla und Gwyneth Molesworth, vermietet ist.
Here it is on Youtube.