Paul , there is not a lot on the Essex side ! There is a slip at North Woolwich ( Barge House Road ) , but in my opinion , only usable at slack high tide , and that's with a 4 X 4 !
If the tides are favourable though , this is only 2 minutes from Gallions Point Marina . ( Lock in and out at HW +/- 5 hours ) .
There is also Poplar Rowing Club for launch/recovery same day but with strong cross tides , if not slack . Otherwise it's up to Putney .
If you fancy the Barge House Rd slip , let me know and I'll check out it's condition ( not used it this year yet ). Bern