I would certainly second Steve.C's comments. Freego Eagles are great.
It has pure throttle or 3 stage pedelec control. With the 17 a/h battery I can ride 45 miles including climbing from sea level over the top of Beachy Head, across the South Downs Way, (chalk, mud, puddles, rocks and steep climbs), down to Alfriston and back home to Battle, and still have 2 lights out of four left on the battery guage, that's with continuous light pedalling. It's a heavy bike, but powerful and handles off road sections surprisingly well. Clearly it is not a full blown downhill racer, but it does me very well for general off road use.
What's more, as it is a legally compliant bike, you can stop off at the pub on the way home and slate your thirst on a few of England's finest ales, then enjoy a leisurely cruise home throttle only. What could be better?
Freego have a good name for customer service, and a proper dealer network,
Another bike I have ridden off road was the EMotion Xenion 650 with Bosch Crank Drive, and this was a really nice bike, and I think if I did a lot more off road riding that would be my choice, but it ain't got a throttle, its a bit harsh on the bum, and on the road it won't keep up with my Eagle.
Just my clearly biased opinion, but it is biased because my Eagle has been so damn good, proof of the pudding and all that!