I've had brushes from Dorian Crafts in Germany. Very good indeed, and another recommendation for Cadman who makes superb brushes.
Happy memories of Rod Neep and Fido of New Forest Brushes, both of whom are regrettably no longer making, but whose products were exceptional and some of the finest made in the UK.
Brad Sears (Brad Sears Brush Works) in the USA has a collaboration with Lee Sabini in London to make Morris & Forndran brushes. You order from Brad, he turns the handle, sends it to Lee who hand ties and mounts the knot in the handle. Lee ships the finished brush from London to the purchaser. I’ve three of the Sears/Sabini M&F brushes and they’re excellent.
Haven't got my hands on one yet but Black Anvil in Ireland has caught my eye once or twice for his handles. Seems to work on a drop type model rather than custom requests.