Hi @rumbero,
You can change the setting in the Magento administration after the install is finished.
Simply install the Magento with the London time, and the when the installation process is done, log in to your new administration and do the following.
Go to:
Admin menu, select System > Configuration > General > General (should be open per default on load)
Click to expand the Locale Options section.
Select your Timezone from the list. Then, do the following:
Set Locale to the store language.
Set First Day of the Week to the day that is considered to be the first day of the week in your area.
In the Weekend Days list, select the days which fall on a weekend in your area. (To select multiple options, hold down the Ctrl (PC) or Command (Mac) key.)
Also check the "Countries Option" while there and fill out "Store information"
Let me know if this helps you any further.
/Kent
-- Best regards --
Kent Christiansen | Magento Certified Solution Specialist