Wow, I always thought the UK was more focused on govt oversight than the US. Here in the US, building inspections have to be organized through government/municipal agencies. Whether they are subcontracted out is related to the size of the city/county but I know in at least 2 medium-large cities (250k-500k people) they have dedicated building inspectors on the payroll as govt employees.

Edit: Of course it would be irresponsible to say that they were consistent. Each inspector has their own ideas of "that should really be 2x12, not 2x10", or "that stairway is too steep", or "that should look more like the other houses", etc. But I do see value in forcing everyone facing a semi consistent set of rules.