Commercial finance in general is not regulated by any statutory body and so commercial mortgages remain largely unregulated.
When considering regulation of finance it is probably easier to consider when a loan is regulated rather than trying to describe when it is not.
- Residential Mortgage lending is regulated by the Financial Services Authority. Broadly speaking this will cover any first charge lending to an individual on a residential property (except buy to let properties). There are other caveats but lets keep it simple.
- Secured loans can be regulated by the Consumer Credit Act 1974 (amended 2006). This covers most second charge loans, although there are exceptions for business people.
Those two are mentioned as they place obligations on lenders (and brokers) about how they do business, along with meaningful sanctions if things go wrong.
There are numerous trade bodies and associations with varying degrees of regulation. The most relevant for commercial finance being the National Association of Commercial Finance Brokers (NACFB).
However it is important to bear in mind that membership of a trade association is usual 95% conditional on being able to pay the fee.