No work competition only one contractor?

A member of my family have purchased a caravan on one of these enclosed sites, where you can pay up to 30k for a luxury caravan, but only get access at the start of the season, and you can use it as a type of little holiday home, hope you get what im talking about here!!! anyway.there seems to be no competition to who does your repairs or any other maintenance carried out on the site, so they can basically charge you what they like without you having the opportunity to get someone to do the work cheaper or at a more competative price, also they seem to carry out repairs and maitenance without your authorisation or consent, is this fair and legal, any & only constructive help and answers would be much appreciated, thanks in advance!!