If it's required in order to make it easier to turn the key the shops which specialise in aids for the disabled (which are often listed under 'Mobility & Access Equipment' in Yellow Pages) usually stock 'key turners', such as these:
http://www.medisave.c...ey-turners-p-422.html
Thanks for that - hadn't thought of the disabled angle. It's actually for my 10 year old son (he has a key to get in when he has been out playing with his mates). Thanks again.