I have been riding for approx 25yrs and never ridden off-road...until last Friday. I did a day in Wales with these guys. https://www.yamaha-offroad-experience.co.uk/ What a day, I did things I never thought I would be dong as an absolute novice. The location is superb with some extremly challenging roads. Day starts at 9:30 and finishes approx 16:00 with a 3/4hr lunch. You finish the day physically shattered, its a full-on day. Instructors are great, the bikes (WR250F or WR450F) are superb. For anyone fancying a challenge and have never done off-road before, have a go, you will be a better rider because of it. Even for the experienced its a great day, in the afternoon they split you up into 2 or 3 groups so that you are riding with people of similar experience/ skill level.
It really is good, frightening at times. I kept sitting back which is completly opposite to what you need to do!