Hi,
Sunday 11th June it is. To get there, take the Southeastern service to London Bridge then the Jubilee line to Canary Wharf. Southeastern trains are not stopping at Lewisham so the DLR option is out.
Low tide is at 1:17PM, so if there is convenient foreshore access, we'll take it. There is a place opposite maritime greenwich:

That tree does grow through the house!
Looking across from the previous photo: