We have an 06 Freelander TD4. Our mpg, calculated as carefully as we can, given the slight inaccuracy of when the fuel refill pump cuts out as being 'tank ful,' gives an average of just over 40mpg solo and about 31mpg with the caravan, which is a 1450Kg approx Sterling Europa 520. The car is always heavily loaded as we carry 2 awnings, windbreak, box of model rc helicopters, ground sheet, foldaway boat, outboard motor and 2 mountain bikes.
Solo, mostly in France, we try to keep our spee to 60mph and travel at 50mph with the caravan. Cutting bacxk by 10mph, over our former speeds, has greatly improved the economy.