Ah ha!
Thanks for that.
By my thinking, the Barbie is more or less 2/3rds as fuel efficient as the Q4, as it has less seats. Burns the same though, but clearly on shorter sectors, it won't be able to get up high enough to cruise efficiently and will be far less efficient.
The more I think, and I know I'll be sad to be turfed of my 146, the Q4 does sound not too far off performance wise, and burns typically half the fuel as a 146 on an hour long sector. 40kts slower is not too bad either. I take it that's barber's pole stuff (we have those things on our old bus you know!)
Certainly it knocks the socks off a 78 seat -100 (bye Bye Scabby Dog!) and G-GNTZ is a waste of space in comparison too at only 79 seats. Hmm.
Shame the hold is tiny! Unfortunately, we make a good proportion of our money underfloor which we'll lose with a Dash. Time will tell.
Thanks for the info though. Food for thought and helps us understand what FlyBE are talking about when they trumpet the virtues of the Q4.