This site sells replacement window keys here : http://www.replacementkeys.co.uk/window
You can also email them a photo for identification if you need help :
http://www.replacementkeys.co.uk/key-identification-help
Jim
March 2011
windowhandlekeys.co.uk have a good advice service
Janet
August 2009
sorry mis-read your question!
you need to go to a web site which provides replacement keys. some show pictures; so if you can visualise the one you lost you may strike lucky.
otherwise you will need a replacement handle which are relatively inexpensive and very easy to fit.
levilewy
August 2009
you don`t.
if there is no key then you need a new barrel and you will need to drill your existing barrel to replace it.
reply if you need to know how to do this
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix windows and doors.