Hi J&G
I tow with a SAAB 9-3 2.2 Vector. Our 'van is an Abbey GTS 416 and we are well over the 85% kerbweight/MTPLM guideline. That said, the car tows well under normal road conditions and I make sure never to over-rev or get myself into embarrasing situations with it.
Unfortunately, the down side is that I have to be very careful in picking sites, both for ground conditions (avoid slippery surfaces/ non-level pitches etc) and those site with slopes, usually CL/CS.
I have found that it is very easy to spin the front wheelsin some conditions.
For these rasons we are, albeit reluctantly, changing the car for something a bit heavier.
I'll be sad to see the motor go as, in general driving conditions (A/B roads & motorways), the car has been great.
As implied further down this post, you need a bit of margin when trying to manoeuvre the 'van, especially at low speeds.
Good luck
John