Thanks Peter,
The noise only happens on very gentle braking at low speeds usually when coming to a halt but not always !!
It only happens for a second or so and sounds like "kerrshoo-kershoo" .
Sometimes it is louder than others.
Definitely not metal on metal - the front pads were changed by a previous owner about 1000m ago.
I had been told by my local garage that this is quite common in Xtypes and is caused by a dirty ABS ring/sensor?
Andy