OK some police don't do their jobs properly, But the majority of British police do a good job (certainly compared to many of the countries I visit)
I should also add that self certs and other variations probably fall into two groups
1. Multiple dodgy applications by BTL'ers for financial gain
2. People (especially youngster's) that cannot afford to buy a HOME unless they exagerate their income
A lot of police would have sympathy for the latter
As for 5 years in prison for mortgage fraud -
if a joyrider with 20 previous convictions kills another road user, they would probably get less than 5 years!