Re reading for the millionth time for a cat b licence.....
Vehicle upto 3500 kg MAM towing trailer 750kg MAM or a larger trailer than 750kg MAM trailer so long as the combined weight (NOT MAM) is less than 3500kg.
So I think I was wrong.....assuming a 90 with some kit in is about 2000kg you can tow up to 1500kg approx.
The licence regs changed again in 2013 just to make it more complicated
The 2013 change for cat b is the larger than 750kg MAM trailer has to have a total MAM of vehicle plus trailer of less than 3500kg MAM.
SO.......after 97, combined actual WEIGHT of less than 3500kg
After 2013, combined MAM (max possible whether loaded or not) of 3500kg