I've never really understood why it's such a problem for you guys.
Out here, people who pull caravans (we call them campers or RV's) use vehicles actually designed to pull them properly, ie.: big V8 or V10 diesel pickup trucks, not pathetic little hatchbacks with four-pots, specifically designed for towing. They can go the normal speed limit (100 kph / 60 mph) and they keep up with traffic just fine.
Someone I know actually owns a semi (lorry) truck for hauling a massive fifth-wheel RV (Three slide-outs, on-board laundry facilities ... the works. Think, that massive RV Top Gear had on their home-made camper-van episode, only it needs to be towed instead of driving itself). The owner is actually a chemist, so she runs it on used cooking oil; I hear it costs about $50 in fuel to drive ~400 miles in that thing.