Generally, ATCers that you speak to only control within 40 miles of their airfield, so are normally quite proficient at good visual reference points such as lakes/railway lines etc.
Of course, London Info ISN'T ATC as such, but a FISO. I would guess they would prefer a generic report (like you say, in relation to an airfield/NAVAID etc)
That said, they know their stuff and you might be surprised at just how much they know!!!