You have three options:
a.) Their 'offical' address at Hollyhead Industrial Estate:
Apple Computer International
Hollyhill Industrial Estate
Cork
Republic of Ireland
b.) Their offices beside/near/same building as the Apple Store London:
Apple
1 Hanover Street
London
W1S
c.) Their famous headquarters in Cupertino, CA
Apple
1 Infinite Loop
Cupertino, CA 95014
United States of America
When I had some problems with my iBook, I write to A and C and got some good results. Does anyone know about B? What part of Apple's operations are in Ireland and what in London?
Seb