Gaz , try the search function , I'm sure this has been covered before . There are surprisingly few B&B options in the estuary itself , especially on the North side . You might want to consider some of the Medway marinas . Chatham can offer B&B and refuelling .
Given the speed restrictions up the Thames from Woolwich , do not underestimate the time it may take from the Medway ( also speed restrictions ) to t'other side of London .
Possible B&B options in St.Katherines ( pricey ? ) or Limehouse ( iffy ? )........