The Londoners began to take control the longer the half went on but were unable to turn their possession into any further points, so had to settle for a six-point half-time lead.
The Welsh club opened a six-point first-half lead through two Hook penalties before Ulster's young fly-half Niall O'Connor, making his first Heineken Cup appearance, reduced the deficit to three points with a 17th minute penalty.
The second quarter was a much slower-paced one, with neither team taking more than a four-point lead and the Wizards scoring the last six points of the half to lead 51-48 at the break.