Some relatively sound advice from Rob
. The only thing I would say is I do dislike this 85% 'rule'. It isn't a rule, it's a guideline but thats all it is. It is a very old fashioned, outdated and un-scientifically tested statement but it gives beginner to towing heavy trailers a baseline to work with as there is a degree in truth behind it - BUT!!!! it's not the be all and end all.
The are far more other factors to consider like loading heavy items low down, the length of the rear over hang of the towcar (the shorter the better), the stiffness of the suspension and anti roll bars (stiffer is better (within reason!)), size of wheels (including the profile) traffic conditions, speed, concentration, weather, tiredness, tyre conditions etc etc.!! I have driven/been in outfits where the ratio was 75% and couldn't even maintain motorway speeds without the fear of turning the thing over. Yet other outfits I have towed up to and over 100% with no issues even in galeforce winds!!!
Prior to my 147 towing this heavy van of mine, I had a Fiesta 1.25 Zetec (petrol) towing a similar ratio of weight to the van I have now. Stability wise that was OK too, although nothing in the league of the 147, but power was more limited. It was always a very rev happy engine solo and on towing duties it required plenty of beans to keep the outfit shifting but it did it and it did it well. Even towing up hills posed no issue. The main problem came when I was towing into a head wind and the lack or torque made the outfit almost undrivable at motorway speeds. The sheer size of the frontage of caravan into a headwind has far more drag than the weight alone!
The 145 1.6 is a Boxer engine if I am right? I beleive this was more torquey than a TS and it came in at lower revs so it will be adequate I'd imagine with the right van. Obviously you need to work out the max tow of the car along with the kerb weight and compare all of this against the unladen wight of the van (MRO) and the maximum laden weight of the van (MTPLM) and see what it all comes out at. Feel free to ask me for a more detailed look at your considerations. Just bear in mind what I said though that you can do all the maths in the world but you never truely know what an outfit is like until you drive it and get to know it!