Is Slow Horses dropping one episode a week? If so I'll wait a month and binge it all in October.
I had to look up "bowdlerisation" - the definition I got was "the act of deleting or modifying all passages considered to be indecent".
If that's what you meant then no, Slow Horses is not bowdlerising le Carre. There's plenty that is offensive and indecent, and the books and show do not suffer from sentimentality.
Gary Oldman is absolutely fabulous as Jackson Lamb and Kristin Scott Thomas is equally great as Lady Di Taverner, although her character is more morally questionable, as opposed to Oldman, who is more physically repellent.
The books are also a treat.
Is it realist? Well, it's more realist than Killing Eve, but not as realistic as Le Carre. It's definitely played a bit more for entertainment. More dramatic flair, less cynicism.