I have had the Cabin Plus since 2012. It’s 56cm tall. I believe the website now says 57cm but it’s the same bag.

I have never, ever had a problem with it on BA. In fact the only airlines to ever make a fuss were MH (who in CDG said it was too heavy but let it on, and on two DL E170s where I boarded late and had to be gate checked or go in the cockpit!)

It fits overhead sideways (not wheels first) in a BA E190 bin although only from about row 2 onwards.

There are many threads on this forum about the bag, it used to be quite popular amongst FTers until they put the prices up!