Hi all, just to confirm that I changed the battery myself this weekend for a Bosch Silver S5005 (type 27). It was very simple to do and the radio didn't need to be recoded (I've just the one touch function on the electric windows to sort). This has completely transformed the car, it is running much better and the steering problem is cured (so far touch wood). So I can only re-iterate some of the above comments that a weak battery can cause a range of issues, one of which would seem to be the power steering struggling. Thanks to everyone for their help.