It is a light weight dainty sports pony. According to my daughter it weighs 350kg, so not much less than the wife.
If she ever reads this thread, you'll need to invest in body armour rather than fixing the car
I agree with what people are saying, there's something else to this Sherlock.
The fact there was "lots of white smoke" sounds very very VERY wrong. At the first sight of any smoke, you'd think the sensible thing would be to stop and think what's going on.
Did the smoke smell? Was it very noxious? Is there any idea where it was coming from? Was it from the exhaust, tyres, engine bay?
"The vehicle is really gutless though even when not towing the trailer."
Eveything is relative, diesel Freelanders may beat milk floats in a drag race, but not a lot else. So if you're comparing to a v12 beemer then yes it will feel gutless, but they'll pull a 350KG load over virtually anything. Is it fact that its down on power? Is there any way to comare against another TD4 to see if its a real problem or just your expectations?
The more I think about this, the more I think that a 350KG + trailer weight is basically nothing. Its like pulling away some KFC regulars on-board!
As I said before, we often pull the sorts of loads your wife was trying to move. I pulled so much weight once the wheel studs sheared on a trailer - it was basically a new trailer, but only rated to 750KG and carrying a LOT more than that - woops! This is with our L Series diesel. The biggest problem I have is that I've trashed both wing mirrors on branches reversing the boat up our drive.
So unless there was an issue with the trailer itself, you can disregard that it was towing anything.
There may be some technical problems here, but I can't help but think there is a sizable amount of pilot error as well (probably too much clutch slipping).