Its one of the easier repairs, June, but you'll need to have the exact machine model number with you when you go searching for one.....expect to pay somewhere in the region of £30 for the part. Try espares.co.uk for mail order? To get access to the valve, the top has to come off the machine - often a couple of screws at the back, and the top slides backwards then lifts off.
John
May 2009