There's the one at Earl's Court in London. Here it is on Google Street View.

Now my favourite part, if you use the arrows to move towards the TARDIS, Street View takes you INSIDE THE TARDIS! :)

Another article here which shows the views from outside as well as INSIDE the TARDIS, if you don't want to have to load up the maps yourself.

It's also possible to do a three hour private Doctor Who Tour in London. Highlights include:

3-hour private tour of Doctor Who sites in London

Visit popular locations from the series covering 50 years

See London’s top attractions in a private black taxi

Enjoy photo ops at each stop (including one with a TARDIS)

Hear lively commentary and fun anecdotes from your private guide

In addition, since the new series started there are several places in and around Cardiff that you can go see, but there's nothing highlighting them, just places you may recognise - for example, Bad Wolf Bay.

There is however, the Doctor Who Experience in Cardiff Bay. It's described as:

An interactive journey that takes you on an adventure through space and time. Step through a crack in time and help the Doctor, armed with his Sonic Screwdriver to escape from his foes, fly the TARDIS and come face-to-face with some of the scariest monsters seen on screen. Featuring exclusive filmed sequences with Matt Smith and packed with amazing special effects this multi-sensory experience is fun for the family and fans alike. After your action-packed journey with the Doctor, there is so much more to see...

It's open daily from 9.30am to 5pm excluding Tuesdays during term time.