Maybe not.
Have a look at this. This document comes from North Norfolk but very similar versions of it appear in various local authority websites across England and Wales. It provides 'Model Conditions of Contract' between a site owner and the tenants.
http://www.northnorfolk.org/licensing/document s/Conditions_Caravan_Residential.pdf
Within the text it talks about the requirement to provide an electricity supply and a requirement not to resell the electricity supplied at a higher price than that charges by the Utility Co.
The point is that your site owner may be in breach of the Planning Consent for the licence to use the site as a caravan site.
The relevant conditions are based on an Act of Parliament called the 'Caravan Sites and Control of Development Act 1960'. Try phoning your local authority and ask whether your site has a planning condition on it that demands the site owner provide the facilities mentioned in the document. Post again if your want more help - I have this thread tracked.