I went from Plata to Blue. There is a special circumstance, though...I got the Plata "for free" with the Icon Visa card. Evidently it was for the first year only. I credit all my IB flights to BA. The only thing that gets credited to IB are VY flights, of which there weren't many Avios this year.
As the Icon card is such a terrible deal, I decided to get an Amex and stop worrying about an airline credit card.