Thanks everyone - all that advice is much appreciated. There is a towing section on the Australian X-Trail Forum and, not surprisingly, they are in general more supportive of using their favourite off-roader for pulling vans, boats and trailers - like this quote from Dave62 which matches our vehicle and likely tow weight "we've got a 2008 T31 CVT, it tows our 14' Jayco poptop beautifully. I know the van's only about 1350 kg loaded but on the Princes Hwy between Gippsland and Sydney it doesn't seem to have a problem. I've always got it in "manual" mode and never have my foot flat on the go pedal, always try to keep it between 3000 and 3500 revs, seems to get around 15l / 100 km at those revs and still sits on 90 / 95". So, despite some negative comments even on that forum, at first I thought we would at least give it a go having assumed since purchase that it would be good enough for a CT. At this stage, it hasn't got a tow bar and brake controller, so Lost's excellent suggestion to ask to tow a demo unit requires us to spend $1500 or so first (and face the prospect of later adding the auto trans cooler and even a suspension mod). But it now looks clearer that while the "Exxy" is (marginally?) capable on a hard black highway standard surface, it is not going to be reliable when the vehicle must work harder anyway, like loose surfaces and steeper hills (at least with 1200kg+ CTs, probably OK at 700kg or less?).
With three months to go before delivery, I have enough time to swap it for something more capable. As someone said on another forum, dealers are used to trading X-Trails from otherwise reluctant sellers who find that towing is not its strong point. I'll be joining that group.
Cheers
Oddy