Well I went ahead with the MK2 ones and they were ordered Friday afternoon and arrived Saturday morning. Tried them on and they seem pretty robust, tried running them under the tap for a minute and didnt get any water coming through. The top part is waterproof nylony stuff.
Though I am a bit concerned at the under strap, which is basically para cord. Im sure after a few hours walking through heather and bracken that will wear through pretty easily.
I see what you meant about the weight of them, seem a bit heavier than expected They also werent tight but then again I have skinny legs and they weren't too baggy.
I wiill see how I get on with them, hopefully get a chance with them next week on my course.