Is the caravan registered in Spain? If not, it cannot be towed, but will have to be loaded on a truck because it won't be covered by third party insurance unless you find someone with a UK registered car to do it for for you.
Thank you for your reply with the information about towing. I bought some plates to put on the caravan so I could tow it myself but I don't fancy the long drive via the channel tunnel on my own so I was hoping to pay someone to help me then get a flight out. The caravan is French registered it is a single axle Hymer Nova 520DB not a large unit. I have towed a caravan in England but my daughter has been with me to help.