Just to keep things straight, a 'Level Bust' is not the same as an 'Infringement' (although it might lead to one !!). Both are separate issues and subject to different awareness and action campaigns by NATS and the aviation industry.
A
Level Bust is defined as:
A deviation of 300 feet or more from the assigned level
This may take one of three different forms:
1. An aircraft in level flight climbs or descends without clearance
2. An aircraft climbing or descending fails to level off accurately at the correct level (either passing through and continuing the climb or descent, or passing through and then returning to the correct level)
3. An aircraft levelling off at the correct level or altitude, but with an incorrect altimeter setting.
Full information on the Level Best campaign can be found here:
NATS Level Best Website
FlyOnTrack is probably the best place to go for GA Airspace Infringement Information :
FlyOnTrack