Hi,
Kerbweights are often difficult to establish, because it will vary according to what optional extras have been included in the vehicle. There are sites that can give 'kerbweights' but you must know exactly what year, make model body style and trim level. Don't rely on close matches, they can can be several tens of Kg different. And I must warn you that many of these sites data bases do contain errors, so do not rely on them being accurate.
Your best bet will be to check your V5 document for the "Unladen Mass" which is as close as you cane sometimes get to an official Kerbweight - unless you actually prepare the vehicle and have it weighed.
Diesel engines are often preferred by caravanner's for two main reasons, firstly as they offer better pulling power compared to the equivalent petrol engines, and secondly they usually offer at least 25% more mpg, But most modern diesel cars seem to use Dual Mass Flywheels, which some people find troublesome when reversing trailers. It is worth considering a auto box if they do one.
With to-days crowded and highly restricted road conditions, the extra performance (Speed and acceleration) of petrol cars can barely be used so diesels are a real alternative. Modern diesels are far more refined and responsive compared to the units traditionally fitted in Taxi's and old vans.