This was an amusing read, but it's certainly fake. A bit of a search around Reddit tells me it's not the first time this particular document has been called into question, and the information it presents as factual doesn't check out.

To begin with, the 'ordinary working classes' of Britain would not have been able to 'speak impeccable and fluent German' to the degree this report claims they did. If anything, they would perhaps have had experience with French at best (as it had been England's unofficial 'second' language during the time of Empire). Considering the obsessive nationalism in genuine SS documentation, I also think an officer writing the following segment would've been shot:

they frequently look better than our own German replacement units. You can see that the uniform they wear is of much better material than the German uniform.

Fashion faux pas from the cult of Hugo Boss? Surely not. All of this leads me to believe it's either propaganda from the time at a generous estimate, or satire from a modern British writer if we take into account a number of potential anachronisms. Using the term 'Herrenvolk' as a piece of independent NSDAP terminology, rather than directly translating it, for example.