It appears that installing Windows 8 on top of XP doesn't give you the option to choose the locale and other settings -- I've got the right keyboard layout restored, and can change the system locale to be for the UK, but there doesn't appear to be any way to change the time zone -- choosing the option to try and change the time zone gives error:

Date and Time

Unable to continue

You do not have permission to perform this task. Please contact your computer administrator for help.

[OK]