I understand the horror of dropping your bike, but what is it that you fear most? Potentially expensive damage to the bike? Or that you won't be able to pick it up? If it's the potential damage, just bear in mind that your 1150 was built for the job and a drop at slowish speed off-road (and by that I really mean a loose or soft surface, i.e. not tarmac or concrete) is likely, at worst, to result in only minor cosmetic damage. Believe me, I'm speaking as someone who dropped their own 1150 at least half a dozen times on unsurfaced Russian roads and had it tipped over in a crate while being trucked across Siberia. OK, it wasn't the most pristine 1150 to start with, but it suffered no obvious ill effects. Those bikes are built like tanks ... Which, of course, brings me to the second point, picking it up after a drop. TBH, although I know the theory and have successfully picked up bikes of varying sizes on the BMW course, there's a big difference between picking up an unladen bike on a flat surface and picking up an 1150 fully laden with metal luggage, spare tyres and camping equipment, when it's pointing downhill towards the camber of the road. Frankly, I'm fairly sure most here would be looking for a bit of help. There's no shame in it.
If you aren't planning to do any more than a bit of trail riding (or riding on unsurfaced roads abroad), a day's tuition and a bit of practice is probably all you really need. I would try to look at the price as part of the overall cost of an enjoyable holiday.
Re the tyres, I'm no expert but I wouldn't use the Tourances on anything but tarmac. I'm sure others do, but part of your lack of confidence on the wet grass will have been caused by a lack of grip. Dual-purpose tyres like Karoos or Heidenaus (which I have, but there are many others) will immediately feel much safer - without necessarily having to go for the full-on knobblies, which aren't so great on tarmac.
P.S. I obviously know nothing about 'trail riding' if the picture above is anything to go by.
