I did this earlier this week with my DSis, we are both R4, R4xtra, Archers fans. I highly recommend it (I have no connection). The 30s building and the new building are worth seeing in themselves and the facilities for the News service is amazing. Portland place also houses the World Service and radio drama. The guides we're excellent, very well informed and fun. We got to "read" the news and weather and did a radio play with sound effects provided by one of the tour group. Do let me know if anyone else goes, or has been, and what you think.