Ok so:
I would go south down to the A1020 roundabout, then head onto the Lower Lea Crossing but just before you join the road there is a cycle path at this point:
http://maps.google.co.uk/maps?daddr=51.508178,0.013062&hl=en&ll=51.508268,0.013899&spn=0.00189,0.003439&sll=51.508218,0.013229&sspn=0.00181,0.003439&vpsrc=6&mra=mift&mrsp=1&sz=18&t=h&z=18
Then head West along the path, which runs parallel to the road, across the bridge. The path ends on a little slip road, cross it and follow the path on the other side, still heading West.
Then what you want to do, once reaching the next roundabout, is go left onto Blackwall Way (or the cycle path takes you onot Aspen way then onot Blackwall ay further up), which is a quiet little access road, follow that onto Baffin Way, across the lights right then left left onto Trafalgar Way which leads you up to CW.
Very straightforward, mainly away from traffic, and will take you about 10 mins. 🙂