Hi JJB,
As with the usual bit of BS in Top Gear (I am a big fan tho'), the paperwork involved in crossing borders was glossed over. You can't just cross over borders without the required clearance - unless you really want to spend a few days/weeks in a rather unpleasant jail.
Anyway, to your question. I haven't driven off-road in Lebanon or Syria, but have done so in Oman, UAE, Bahrain, Saudi & Kuwait. It's totally different to dear old Blighty as we tend to take things slow here. However, in the M.E. you have to go a lot faster or you just sink down to the axles. Soft sand is great fun, and the dunes are magnificent (until you get caught in a bowl and have to do the wall of death), but the scrublands you saw are full of razor sharp rocks and stones that'll rip your tyres to shreds and kill the suspension. Even soft sand has its hazards, on one "expedition" in Saudi, a fellow driver flew over the top of a dune and landed straight on a rock which bent his Patrol like a banana! It kept on going, but looked most peculiar when we found some tarmac.
On the subject of vehicles, this is probably where I get blacklisted. I've always had a Landcruiser Amazon (which the Arabs call "Donkey") for off-roading in the M.E. and it has never let me down. I've dragged Rangerovers and Discos out of trouble - but never a Defender.
In short, give it a go, great fun (and a real sense of achievement) - but NEVER on your own. I'd recommend at least three vehicles, and watch out for those camel spiders!!
Good luck,
Peter