Thank you for your considered answer RA. I was mightily surprised by what happened and even with my limited aeronautical experience, I knew something was abnormal. I'm not sure if we were anywhere near MTOW as the aircraft had a Shadin instead of the normal fuel gauges. Pax, bags and pilot weighed about 480kg I reckon.
CLose examination on Google earth shows about 3400ft ground roll, about 1200ft uphill at say 1.6% and distance to high trees 1600 ft. past end of strip.