I'm unfamiliar with the licensing for the building trades in the UK. Are you studying for a general contractor's license? electrician? It seems like you have such a large number of areas that require your competency with these exams. It also sounds exhausting.
There are many trades all of which have their own regulatory bodies (various choices for each trade). For instance, if you are an electrician you have to subscribe to either NICEIC, Elecsa or Napit. By doing so they sort of underwrite you/your work and you can operate freely. If you are qualified but aren't a member of one of those, you have to notify Building Control who are part of each local authority and they will inspect your work and sign it off - for a fee.
For gas, there is only the Gas Safe register but other elements of this field of plumbing, that doesn't involve gas, has other options much like what I mentioned for electricians. At the moment (I passed today's exams btw which is what's called CENWAT1) I can either sign up to someone so I can install, commission or service cylinders, or wait until I finish the big one (the Gas Safe CCN1) and that will allow me to register my work on cylinders through Gas Safe.
Not all work within many trades is regulated or needs certification so in the main you can just crack on, but, with the ever broadening energy saving and field of 'renewables', you have to keep one eye on how regulation may have changed and may have sign up to a body to be able to continue.
I could end up paying many of thousands each year just in subscriptions.
This is a video that constantly does the rounds in the area I qualified for today:
