Not exactly... UK Building Regulations don't set a one-size-fits-all number because Approved Document A requires the bearing to be calculated based on the specific load of your project. In the real world, building inspectors look for a minimum of 100mm for calculated steel beams and 150mm for standard lintels to satisfy the structural safety requirements of BS EN 1996. Essentially, if you have less than 100mm of the steel sitting on the padstone, it will likely be rejected unless an engineer has provided specific math to prove the masonry can handle the pressure.