PM David Cameron put on an Aussie accent when he repeated what Australian PM Julia Gillard had said to him at a recent Commonwealth heads of government meeting. He was talking about a very recently passed law here in the UK which will ensure that the first-born child of Prince William and his wife Catherine, whether a boy or a girl, will be the next in line to the throne after William. Julia Gillard said it was good news for Sheilas everywhere.
Sheila is a generic word for young woman in Australia. The OED says it is 'playfully affectionate and predominantly in male use'. Sheila is an Irish name (can also be spelled Shelagh) and was often originally used in Australia to refer to any woman, where Paddy would be used to refer to any man. The first citation for Sheila in the OED, from 1828, is "Many a piteous Shela (sic) stood wiping the gory locks of her Paddy, until released from that duty by the officious interference of the knight of the baton".
You can see and hear the David Cameron video clip here (the Australian accent is at the very end).