Many thanks to Mike and Darren for replying. Thankyou for your reassurance on the cooling system operation Mike. Top marks must go to Darren. A concise and professional response as usual. (I've booked an appointment at the opticians). A pity that the Rover partsperson couldn't find the replacement sensor as quickly. The colour has changed from black to blue. I will post the new part number tomorrow, might save someone the hassle that I've had. Regards, Steve.