I used the Woolwich ferry today and whilst it was alright (it is free after all), I want to keep my legs and cogs spinning. I'm not sure the ferry operators would be all that impressed if I started cycling around the cars parked on the vehicle deck. The Woolwich tunnel is a bit annoying at the moment though, as both lifts are out of operation and the stairs would make even the fittest person sweat if they were carrying a bike!
On a side note, it did make me laugh that there was a "Cyclists Dismount" sign at the end of the "non-rideable" tunnel and the bottom of the stairs. Who is that sign for?