Lcy to M25 commute north by m11 is about 25mins on average. Rush hour trying to get over the A13 can be about 45mins. Most duty's finish and start at times that make it a bit easier. Going south is a bit more of a lottery!. you can take the A13 then cross at dartford, or the blackwall tunnel then appropriate route, or take the ferry then the A2. 95% of the time it will be easy but it only takes one problem at the end of the m11 or on the A406 to add 30mins onto the journey.