Just to build that agree's with all the positives but from a slightly different perspective.
I went to the Triumph Adventure Centre just over the road from the BMW one, mainly as I was considering a Tiger 800. The courses will to some extent be similar and I did level 1, level 2 and then a 2 day gravel tour within 6 months, and went from being someone with zero off-road skills, to being able to ride a 200kg+ machine off road in some pretty wet off road conditions (albeit with a slightly dented bank balance).
I've since been back this year to do a days 'level 2' trail riding on the new Tiger models. I absolutely loved it, and went on to buy a Tiger 900 Rally pro earlier this year. I will do a level 3 and probably another gravel tour with them next year.
I've driven every time, as like the comfort of heated seats and a dry environment afterwards, and haven't stopped over after (even though Ystradgynlais is a 180 mile journey).
I stayed at Cwtch farm, which is a nice small B&B, but a little bit isolated (
https://cwtchfarm.co.uk/ ). There is a nice Tesco's and chain pub at the back of the industrial estate, and if they are open I do like the steak house 'The Aubrey Arms' which is on the roundabout as you head to the training centre.
I would have gone the BMW route all things being equal, it was only as I was looking at buying a Triumph that I went that way (I'm not saying the Triumph one is in any way better as can't directly compare). I posted briefly about it
here.
The one thing that amazed me was how capable the bikes were (I watched the BMW ORS trainer take a GSA up a rocky climb on tickover like he was riding across a
's car park). These bikes are never the limiting factor.
RBW.