Here is a little clock of the time and date in London.
The time zone in London is GMT/UTC 0. Daylight saving occurs on the Sunday in March and daylight saving ends on the last Sunday in October.
This means that clocks go forward in Spring (add an hour in March) and clocks go back (minus an hour in October) in Autumn. The clocks going forward is called British Summer Time and the clocks going back in October is called Greenwich Mean Time.
More information on this can be found at the site below, also if you are visiting London it is well worth visiting the actual Greenwich Mean Time Line in Greenwich.