According to the site Jedi News the film has been in pre-production at Pinewood Studios for three and a half months in advance and will start shooting in August 2013. Also check out the production title for Episode 7...
We just got news from a very trusted source that a filming location deal was signed a couple of months ago and studio space and facilities have been block booked for the next ten years at Pinewood Studios.
In a move similar to the Prequels (JAK Productions) and Return of the Jedi (Blue Harvest Productions) the film is in pre-production under a pseudonym: Foodles Productions Ltd, a company registered on 26th March 2013 to the Disney headquarters in London.
Further to this we understand that the film has been in pre-production at Pinewood Studios for three and a half months in advance of an August 2013 shooting date. We hear they have block booked the studios for 10 years and that construction of offices and facilities on-site is underway. Also storage space is being located in the local area.
Previous reports were that filming will start in early 2014. If they really start so early in August then I believe it'll be for pre-shoots, test and scenes not involving any characters. We just have to wait and see. For now take this rumor with a pinch of salt.