beckster

i own a house in london with a friend and am heading to sydney in January on a 2 year work visa, we've agreed that i will rent out my room and pay any short fall between rent and mortgage (hopefully won't be any!). the bit we're not sure about is whether we need to tell the mortgage company, it's not being sublet as she'll still be there and i have a horrible feeling they'll want tonnes of information etc. anyone out there got any ideas or experience on this one? i realise i need to tell the life insurance people but would rather not tell the building society.
thanks!