HI Rob.
Your Honda should be perfectly fine. But that's not the point.
The trader who sold you the caravan should of made sure the van displays it's max permitted weight as this is a legal requirement.
To satisfy yourself that the van is legal behind your car, load it with about 200Kgs of holiday gear. You know the stuff, awning, groundsheet, peg box, aqua roll& waste master, 25Mtr power lead, spare wheel, jack, and then a weeks clothes and a couple of days of food for 4 and you'll soon use 200kgs of pay load. Then take the outfit together with all the family and the dog if rover goes on holiday, together with a full tank of fuel, to your local public weigh bridge.
You should weigh both the caravan on it's own and then the car & van & all occupants including you the driver. This will obtain the gross train weight of your car & van which then compared with the weights stated on your vin plate should be lower than the highest figure quoted on the vin plate. If you are not sure of the weights, go to your local Honda agent for advice.
You will also now have a weight of the caravan in it's maximum expected load state. How ever this is only a guide foryour reference. Now what you have to do is get in touch with Avondale and by stating your van model, they should be able to advise hteir weights for the van and for a bit of your hard earned they should be able to supply a replacement plate.
Just a thought, but on my van there is a chassis a manufacturers plate attatched to the A frame but tucked away right under the van where the A frame joins the main chassis, have you checked there?
Good luck.
Steve L.