Hi Andrew,
My sources suggest that the Astra 1.9 only has a maximum tow capacity of 1300Kg
Based on the figures you have supplied, Your Astra can tow the Coachman, BUT, you will not be able to load the caravan to its full capacity, as that will exceed the cars rated towing weight.
You will have about 180Kg of available payload, which must include your battery, gas bottles, all you personal items.
You must not exceed the cars rated towing weight. It all seems a little boarder line. Also if this is your first caravan towing experience, it is better to aim at 85% caravan to car weight.