As others have said, crack on. You are not responsible for others not paying attention to or not understanding the signs.
You probably got the same looks and head shakes that I get everytime I travel down my own private lane on the M42 south after the airport!
Crack on as others have said. I also use bus lanes depending on the time and day of course 
how many times do we see where a lane well ahead has been closed and virtually all go into one lane leaving the other empty
if they did not want drivers to use the empty lane then they would have prevented drivers from doing so
what they actually want is for all drivers to fill up both lanes then merge at the closure but drivers seem to want to ignore this piece of common sense
I wish we had the zip merge law here
ROG:
how many times do we see where a lane well ahead has been closed and virtually all go into one lane leaving the other emptyif they did not want drivers to use the empty lane then they would have prevented drivers from doing so
what they actually want is for all drivers to fill up both lanes then merge at the closure but drivers seem to want to ignore this piece of common sense
Don’t give them ideas, I save tons of time on my journeys bombing down the empty lane.