if no wifi available on site, check your mobile phone. if you're on a contract that allows you internet access use that and a bluetooth connection from your mobile to your laptop. If you don't have a contract like this you can dial any of the free access ones like 08451232000 and pay 20p minute or similar. Sounds expensive for browsing but adequate for checking emails etc. If your phone is Nokia, load their PC Suite onto the laptop and it will take care of the connection for you but then your charges will be whatever your mobile airtime supplier charges you for internet access instead of whatever they charge you for an 0845 number. hope this helps Tom!
You might be able to get a signal to your caravan site via satelite plus some eqquipment that will make thisa work and use that to connect to the internet but you will still need a wifi enabled lap top.