It appears that Claire Bloom was indeed playing the Doctor's Mother!!
Well in Russell T. Davies's mind at least. Who knows what Steven Moffat will decide to do with that if he ever brings her character back.
The story was just posted over at Life, Doctor Who and Combom and the information was taken from the newly released (in the UK at least) Doctor Who The Writer's Tale The Final Chapter .
I'm waiting to get my hands on this book here in North America hopefully by the end of the month.