Start - Settings - Control Panel - Date, Time, Language and Regional Options - Add other languages - Details button - Under 'Installed Services' click 'Add' and in the top box choose 'English (United Kingdom)', click OK, select the 'English (United States)' option and click 'Remove', click 'Apply', select the US option again and click 'Remove' and click 'OK' once, select the 'Advanced' tab, select 'English (United Kingdom)' in the drop down box at the top, select the apply all settings to current and default user profile, and confirm, and click OK.
Job done. Per user setting though, so you'll need to change any other users on the laptop if they're configured.