no I specifically asked them about MAM and they said as above it is the weight of the combination not the MAM of the combination, the MAM rule applies only if the trailer is MAM less than 750kg in which case it's that + 3500kg MAM to give 4250kg MAM.
This was the area of confusion hence why I asked them specifically this question and got the above reply, unfortunately I'm not able to copy my original email but I specifically told them the date I passed my test, my driving licence number, the unladen weight and MAM of a 110 csw, the unladen weight (guessed 350kg) of a sankey and the MAM of 1100kg for the sankey and they replied as above you can tow it but only to a combination of 3500kg
I am lucky in that I doubt I will ever need to carry more than a ton of stuff with me but obviously the 3500kg weight restriction would be very limiting to some, ie if you wanted to tow a car somewhere for example
It could all be made much simpler!