I stuck with the smallest size because I figured I'd need a third ball for the next size up, but because I used larger needles than called for I think the beret turned out somewhere between fitted and regular, which is perfect.
Pattern: Gretel by Ysolda, fitted size.
Yarn: Rowan Felted Tweed Aran, ivy, 2 balls.
Needles: #6s for the ribbing, and #9s.
I think this beret looks great knit in a proper tweed, too; I'll knit one for myself in Kilcarra eventually. (It's one of my favorite yarns, from a mill in County Donegal.)