As Richy says. It is what the manufacturer specifies and it works a treat for me.
For towing, consider getting a full-size spare wheel for the car and adapt the bootwell as necessary. I don't believe you should tow a 1500kg trailer with the squirty foam or a spacesaver as a very temporary repair. If you are off on holiday the thought of trying to find a tyre 'shop with a caravan on the back doesn't sound like fun (particularly if you have a ferry to catch).
2015 2.2 CDTi SENav 163ps manual 4x4 in Carbon Flash with 19\" alloy spare towing a Bailey Unicorn III Madrid @ 1500kg.