At British Grand Prix Race

Keanu Reeves' onscreen need for speed became a reality this weekend -- he's in England taking in the Grand Prix race ... and seems to have an allegiance for one team in particular.

The actor was out and about Saturday at the Silverstone Circuit, where F1's British Grand Prix is underway ... surfacing at none other than the Aston Martin garage, where KR was watching the team's lead driver, Sebastian Vettel, take the wheel and zip around the track.

Keanu, who tends to be pretty private, was hard to miss ... and didn't seem to be shying away from the attention. At one point, he was photographed with raceway earmuffs while hanging out with AM crew members and staff -- who welcomed the guy with…