For those of you interested in England's built heritage, there are 2 great weekends in September when you can visit places for free.
For everywhere outside of Greater London the Heritage days set around the 2nd weekend in Sept can be viewed online via this website. Heritage Open Days. I'm afraid there isn't an app for this.
On the 3rd weekend of Sept, buildings in Greater London are opened for free access. There is a paid app for this. The 2013 version is yet to be released. However check this link Open House London. I don't have any photos toots of past visits, but I can assure you that you will get a great welcome from helpers and staff at the buildings.
In fact you should get more sizzle for you sterling!