As a fan of festivals and camping, I came across this great article: http://www.perfectpitchmagazine.co.uk/pitching-up/advice/182-overloading-your-car-insurance-and-fines
I did worry that weighing my car down with passengers and heavy camping equipment would have an adverse effect on my fuel consumption, but had no idea I could run the risk of getting fined or possibly have points taken off my licence.
Have a read, it's very illuminating!
Read the above article, answer to it all.....Don't go camping, book a nice hotel.