As Globaliser has said it is quietist when if has it;s mandatory 24 hour shut down from 12.30 pm Saturday until 12.30 Sunday.

As you have a destination in mind then you can choose a quiet time but you are really set by the flight times. I have used LCY at most times of the day - and even at the peak times (any weekday before 9am and between 4.30pm and 9pm) and it never is a problem to get through. An as no BA lounge no need to get there much more than 1 hour in advance.

If you can get an LCY flight at the price you want then don't let the time put you off even the lack of any fast track security does not make the experience uncomfortable.