^What do you mean about liberties being taken with locations?
I've only watched once so might be wrong, but the ones that popped out were:
* Highgate. Less manicured and more overgrown, rambling. But I guess they either weren't allowed to film there or didn't want to.
* Baker St. Not sure where they filmed that. But filming at actual 221b (which I think from memory is a museum/tourist trap) either not practical (it's a busy main road) or they wanted something more hipster.
* New Scotland Yard. I'm sure we saw an establishing sign, and then the next minute they're by the river several miles away overlooking Tower Bridge
. Again, that's probably impracticality of real location, and production desire to get a cool riverfront shot that screams 'LONDON'.