I've just travelled from Mile End in East London, along the Regents, along the Paddington Arm and down the Grand Union to Brentford and onto the Thames. Just thought I'd add my experience to this topic in case it helps someone in the future.
At a pretty tall height of 2.45m my boat cleared all the bridges easily and I would say that even at the lowest bridges there was a good 15cm+ to spare. CRT's updated dimension data does now show a max height of 2.67m on all those waterways so I'd say this is pretty accurate. Also, the water was pretty much at its highest.
Worth mentioning though that I'm only at 2.45m tall down the middle - I have the profile of a regular trapezium! This means arched bridges aren't a problem for me, but if your boat is the same height all the way across and you have a wide beam then you may have some troubles.
Hope this is helpful to future researchers!