I am a regular on the tidal part of the Thames and if you want to explore this area I would suggest you launch downstream. The best all-tidal site in Johnson Drawdock on the Isle of Dogs and there are several others around there but there are tidal restrictions. Greenwich Yacht club has a good facility. Check out www.boatlaunch.co.uk
for all the details.
Check the tides since launching or recovering when the tide is running fast can be tricky. The main thing to look out for is plastic bags that wrap themselves around the water intake and can cook an engine very quickly. If you do not have over heating alarms fitting, get them on before going on the Thames. I speak from bitter experience. There is also a lot of drift wood. That said, it is great fun going under Tower Bridge and past the Houses of Parliament and it is a great way to see London.
Unfortunately I cannot make 22 Feb, but if you go for a later week-end I would like to join you.