Hi Timothy.
I looked into doing this test my self, As I also fall into the category of having eventually to sit a Caravan & Trailer test as it is called.
It's pretty basic, As I am led to believe from the instructor at my local LGV or HGV learning centre, All depending on your driving experience, You book your lesson by the day, So for example if you have not towed a Trailer or Caravan before you would probably need two to four days instructions with your test on the next day, The prices may vary from place to place but I was quoted around