Anyway, so back to the 7650. Still a marvellous phone. Shame it doesn't support voice profiles for Bluetooth or I'd still happily use it. If I call one particular friend, whether using the stored number or dialled by hand on the keypad, I get what appears to be an adult premium rate number (ie "Hi, this is Sophie..." and so on, something about her having a horny female friend was as far as I got before hanging up). Yet, if I call him from the land line, it all works. Weird, huh?
Orange tech support were impressively puzzled but could offer other suggestion other than to send me a SIM update. That said, it seems to have done the trick. Still deeply curious to know just was happening!