Well... that depends on the size of your brisket and the temperature going into the oven, doesn't it? Assuming 5-6 lb brisket, I'd start at 300, check at 2 1/2 hours and go from there. It will likely need another hour.
In general, that is consistent with most braised brisket recipes. Gordon, no matter what he may say, isn't really cooking it "low and slow" as American BBQ would define it.
In terms of oven temps, that range is considered "a slow oven" in the old school terminology of oven temps:
My BBQ experience is with a Webber charcoal kettle, 22 inch model For brisket, I/ use a snake configuration, two layers deep, all the way around the fire grate. For brisket, I'm putting chunks of alder, maple, or birch on top of the coals. Place a disposable aluminum roasting pan in the center. Light one end of the charcoal snake. Make sure it is completely ignited. Place the cooking grid on top, rub the brisket with your preferred rub, and place over the drip pan. Oh, have drip pan half filled with water. Put lid on and adjust all vents fully open. Inset a meat thermometer stem through one of the lid vent holes. You are shooting for a BBQ temp. of between 290, and 300' F. Adjust vents accordingly Use broadcasting thermometer set to 290 F. with the probe inserted to the middle of the thickest part of the brisket. Walk away. Baste if you must at 30 minute intervals with your chosen basting solution, until the thermometer reaches the target temp. Remove the brisket, and let rest for 20 minutes before carving. /Use the liquid from the drip pan for sauce, or gravy.
Watch the thermometer that measures the Webber cooking temp. Add more charcoal to the snake as needed.