How can I fix my BOSS BR1 turning on the boilerin the night?

My boiler is switching itself on overnight when the main timer (British Gas UP2) is off.
When I get up at 3:45 AM the light on the LED indicator on my BOSS BR1 is on and at 4:00 AM the boiler ignites. on checking the UP2 timer control there are no lights on.
When I check the BG UP2 timer settings the CH and HW shut off at 11:00 PM.
I cannot understand how the BR1 LED indicator can come on when the mains are off.
any help would really be appreciated.